Please critique: My plan for configuring 4 hard drives in Mac Pro

[jasone6]

I've had my Mac Pro (8-core, 2.8GHz) for almost a year. I just purchased two more hard drives to fill the remaining 2 bays -- for a total of 4 one-TB drives. My data is backed up, and now I'm ready to start completely fresh. I've done some research -- much of it at diglloyd (http://macperformanceguide.com/) and I'd like some feedback on my plan.

I put together a graphic to show what I've got in mind. A couple things to note:

- I prefer to have an internal Time Machine backup
- I know 2-drive striped RAIDs double chance of failure
- I know Time Machine should be 1.5x (or more) the size of the data volume, but I don't plan to use all the data volume, so it should be fine.
- One drive is Hitachi (from Apple), and remaining 3 are Samsung F1

Aside from general reactions, I'd love to know if there are any special considerations in setting up my striped RAIDs. I've never set up RAID configurations before. Partition Table considerations?

Thanks!

-Jason

155286

[UltraNEO*]

Just my option...
Having two sets of striped drives doesn't make for good redundancy, if your gonna use the additional drives for backup it makes more sense to keep them as single volumes.

Seriously, using stripe drives is a accident waiting to happen.
The only benefit from having striping is speed!!

[sidewinder]

I don't think the plan is good at all. Using RAID 0 these days makes no sense. Especially for a Time Machine volume. You are just asking for data loss.

I would instead opt to use RAID 1+0 (mirrored then striped) using the four 1TB drives. Then I would get an external 1TB or 1.5TB drive for Time Machine.

Ideally, you will have a spare 1TB around in case a drive in the RAID 1+0 array fails.

Heck, I think you would better off going RAID 1+0 with no time machine than with what you originally planned to do.

S-

[gibbz]

While the performance isn't the greatest, I have been using RAID5 in my Mac Pro. You could use it with 3 or 4 drives. I guess since you want an internal drive TM, you could use 3. You would basically get (N-1)*Smin storage space .. so in your case 2TB of useable space. So if you limited what you had TM backup, you could use the 4th disk as the backup.

It seems that RAID6 is becoming more recommended over RAID5 in a few articles I have read.

[Trip.Tucker]

<snip>

It seems that RAID6 is becoming more recommended over RAID5 in a few articles I have read.

Which articles? There are far superior redundancy setups like 1e or 10a1 etc rathern than RAID6 which has been around as long and RAID5 and yet has not been adopted en masse.

[jasone6]

Just my option...
Having two sets of striped drives doesn't make for good redundancy, if your gonna use the additional drives for backup it makes more sense to keep them as single volumes.

Seriously, using stripe drives is a accident waiting to happen.
The only benefit from having striping is speed!!

I understand that having a 2-disc striped RAID for the "data" volume makes for twice the likelihood of losing data, and I understand that having a similar 2-disc striped RAID for Time Machine means the same.

That said -- for me to lose all my data, 2 separate drives would have to fail at (or near) the same time, right?
- I also have 2 external 500 GB hard drives (for a total of 1-terabyte) backing up my most important data via a non-Time Machine backup program.
- I also use an online backup service for my super-most important data
- I also burn photos, music, etc. to DVD and store in a fire/water-proof safe.

So -- assume that Time Machine is important to me -- but not the end of the world if it fails. Does it make any more sense now?

I've read about other RAID configurations, but its confusing to me. This seems simple enough, moderately reliable, and very fast. Am I off base?

Thanks for the responses...

-J

[Trip.Tucker]

I understand that having a 2-disc striped RAID for the "data" volume makes for twice the likelihood of losing data, and I understand that having a similar 2-disc striped RAID for Time Machine means the same.

That said -- for me to lose all my data, 2 separate drives would have to fail at (or near) the same time, right?
- I also have 2 external 500 GB hard drives (for a total of 1-terabyte) backing up my most important data via a non-Time Machine backup program.
- I also use an online backup service for my super-most important data
- I also burn photos, music, etc. to DVD and store in a fire/water-proof safe.

So -- assume that Time Machine is important to me -- but not the end of the world if it fails. Does it make any more sense now?

I've read about other RAID configurations, but its confusing to me. This seems simple enough, moderately reliable, and very fast. Am I off base?

Thanks for the responses...

-J


You're not really that off base. You can run striped volumes and you will have the same risk of hardware failure as if you ran a single hard drive. The unfortunate compounding result with a striped set is that if one disk goes you lose all data on all disks due to the way the data is written. In some respects, you increase your redundancy by running one drive instead of two in a stripe set.

What you can consider is an external drive with your "absolutely, cannot lose this" data on it. Then go crazy with different setups internally. You'll allow yourself more freedom to play with different setups.

[jasone6]

...The unfortunate compounding result with a striped set is that if one disk goes you lose all data on all disks due to the way the data is written. In some respects, you increase your redundancy by running one drive instead of two in a stripe set.

What you can consider is an external drive with your "absolutely, cannot lose this" data on it. Then go crazy with different setups internally. You'll allow yourself more freedom to play with different setups.

Thanks Trip. I understand that if one drive fails, I lose all the data within it's counterpart in the striped RAID. Having said that, if I have a second striped RAID acting as Time Machine, for example, then even if I lose a single drive within my main array, I'm still covered (via TM), right? Likewise, if one of the disks in the Time Machine array fails, I lose all of Time Machine -- but I'd still have my main data array, right?

As I understand it, I'd have to lose a drive in EACH of the 2 striped RAID arrays (1 in the main data array, and 1 in the Time Machine array), to lose all my data (notwithstanding what I've backed up to my externals).

I'm having trouble understanding how this would be a less desirable setup than a RAID 1+0. In that setup, I'd also have to have 2 drives fail to lose my data. And, like in the setup I've proposed, there would be a chance that I could get lucky if the 2nd failure came from the right place. (In my scenario, that would be if the 2nd failure was part of the same striped RAID; in the RAID 1+0 scenario, that would be if the 2nd failure was part of the other array. Right?

[jasone6]

I don't think the plan is good at all. Using RAID 0 these days makes no sense. Especially for a Time Machine volume. You are just asking for data loss.

I would instead opt to use RAID 1+0 (mirrored then striped) using the four 1TB drives. Then I would get an external 1TB or 1.5TB drive for Time Machine.

Ideally, you will have a spare 1TB around in case a drive in the RAID 1+0 array fails.

Heck, I think you would better off going RAID 1+0 with no time machine than with what you originally planned to do.

S-
Thanks sidewinder. I'm interested in your input, but I'm having a hard time understanding why a 1+0 with no Time Machine is better than my proposed configuration. It seems like it has exactly the same probability of total data loss (not to mention the multiple versions of backed-up files that Time Machine keeps).

Thanks again... would love to understand where you're coming from.

-J

[Umbongo]

Thanks sidewinder. I'm interested in your input, but I'm having a hard time understanding why a 1+0 with no Time Machine is better than my proposed configuration. It seems like it has exactly the same probability of total data loss (not to mention the multiple versions of backed-up files that Time Machine keeps).

Thanks again... would love to understand where you're coming from.

-J

With your proposed solution if a drive goes on the first array you will lose your data. So would need to restore it from Time Machine and backups. If one goes on the second array you will need to reinstall your software and OS, and you will lose all your time machine backups.

If you had everything on a RAID 10 setup, then if any single drive went you wouldn't lose anything. You could just put a new drive in and rebuild. If a drive also goes on the other RAID 1 (RAID 10 is two RAID 1s striped) then you would be in the same situation as above, you would just replace both drives. You would need to have both drives from one RAID 1 go to lose data. Therefore it has better fault tolerance.

You would want to use an external drive for time machine (and possibly back that up nightly/weekly to another of the same size for even more redundancy). You of course only get 2TB of usable space on internal drives this way.

[TuffLuffJimmy]

Why would you have two sets of striped drives? I can understand having it for your main drives, but it makes no sense for Time Machine. It'd be a lot smarter if you had it set up like this:

Drive1 and Drive2= striped
Drive3= time machine of your striped drives
Drive4=mirror of drive3 (or a mirror of drive1 and drive2)

[sidewinder]

You can run striped volumes and you will have the same risk of hardware failure as if you ran a single hard drive.
Not true. A two drive RAID 0 array is twice as likely to fail as a single drive. A three drive RAID 0 array is three times as likely to fail as a single drive. And so on and so on.

S-

[jasone6]

Why would you have two sets of striped drives? I can understand having it for your main drives, but it makes no sense for Time Machine. It'd be a lot smarter if you had it set up like this:

Drive1 and Drive2= striped
Drive3= time machine of your striped drives
Drive4=mirror of drive3 (or a mirror of drive1 and drive2)

Your suggestion would be great, except that Drive1 and Drive2 striped = 2TB, so unless I stripe the 2nd set of drives, I'm looking at trying to backup a 2TB volume with a single TB drive/volume.

[jono_3]

go raid-5

[sidewinder]

jasone6,

What you want to build is something that can survive a single drive failure with no down time. RAID 1+0, also called RAID 10, provides that.

In fact, with RAID 10, you could lose two drives, one in each mirror, and everything would still be running. If that happened with your proposed setup, all data would be lost.

You still want to have a Time Machine drive and a spare drive for the RAID 10 array.

S-

[sidewinder]

go raid-5

Then he needs to buy a RAID card, right?

S-

[Umbongo]

Then he needs to buy a RAID card, right?

S-

Yes.

[rylin]

- One drive is Hitachi (from Apple), and remaining 3 are Samsung F1


This is by far the biggest problem; especially if going with RAID-5.
What it boils down to is that you want the disks to differ as much as possible, given the same size.

The most resilient RAID setup is two or three different brands with disks all of the same size.
If you need more disks than you have brands, try to get disks manufactured from different factories, from different lots, with differing production weeks.

The biggest problem with RAID-5 is that parity (which is used to calculate the real data if it goes missing) is spread out over all disks.
This means that when (no, not if, sadly!) you need to repair the RAID, you're already at a very degraded state, making the remaining disks be read from constantly for *hours*.
This, in turn, makes it much more likely that one of the remaining drives will simply toss in the towel.
I'm glad to say I've used RAID-5 for the last time.
That was with 24 300GB SAS disks (or, well, 9x300 R5, 12x300 R10 and three global hot spares) . The smaller disks and the more solid hardware helped when there was a problem.

If you really want to do something non-wasteful, wait for Snow Kitty and use RAID-Z.
It's less computationally intensive and smarter in every single way, given it's tied to ZFS.

Personally, my next project is likely 6-8 drive AoE storage with ZFS on RAID-10 or ZFS on RAID-Z.
It doesn't get much better than that unless you're using a Centurion to pay for storage ;)

[sidewinder]

This is by far the biggest problem; especially if going with RAID-5.
What it boils down to is that you want the disks to differ as much as possible, given the same size.

The most resilient RAID setup is two or three different brands with disks all of the same size.
If you need more disks than you have brands, try to get disks manufactured from different factories, from different lots, with differing production weeks.
While I appreciated the idea, it makes very little practical sense. Look at RAID arrays high density storage devices in data centers across the country and you will find that at least 90% of them are built using the same exact drive model. The majority of those are built using Seagate "NS" drives.

I guess it is worth while to try and get drives built at different times. But the reality is that is rarely an issue.

The most resilient RAID setup is built using the best drives available. Most vendors agree that those drives would be Seagate "NS" drives. My personal experience managing a data center for 10 years would back that up. Yes, Seagate had a problem recently with some of their drives. But that is the first time I can recall such a problem and it was resolved quickly enough.

S-

[jasone6]

jasone6,

What you want to build is something that can survive a single drive failure with no down time. RAID 1+0, also called RAID 10, provides that.

In fact, with RAID 10, you could lose two drives, one in each mirror, and everything would still be running. If that happened with your proposed setup, all data would be lost.

You still want to have a Time Machine drive and a spare drive for the RAID 10 array.

S-

Actually, I don't really think those are my needs. "No down time," would be nice, but isn't my main concern. And while you're right in saying that I could lose 2 drives -- one in each mirror, and still be fine -- I could also lose 2 drives -- both in one mirror, and be fine with my current proposal, right?

I appreciate all the input everyone's been giving. I don't want to buy any more drives or a RAID card. As I see it, my choice is between:

- my proposal: requires 2 drive failures for complete data loss -- possibly 3 (if I get lucky)
- RAID 1+0: requires 2 drive failures for complete data loss -- possibly 3 (if I get lucky). Doesn't provide benefits of Time Machine (i.e. multiple versions of saved files)

I hope I'm not coming across as being argumentative. You guys clearly know a lot on this topic, and I don't. I'm just trying to arrive at an understanding and have yet to see how my proposal is statistically more prone to failure. Any further input is greatly appreciated.

-J

[Horst]

2 x 1 TB drives in striped Raid are ca. 1TB in total, aren't they ?

Imho there is nothing wrong with Raid0, in combination with partitioning you get super fast drives for little money, and it's easy to set up.
For batch processing and scratch, it's hard to beat.

The scratch partition I'd keep bigger, depending on your workflow and file sizes you might run out of space there ; data storage using Time Machine might not be convenient, as TM is only doing incremental backups.

My own internal data drives only contain stuff I'm working on, everything else is manually backed up (twice) on external drives when I'm done with it.

Not as save and convenient as a mirrored array, but again, it's simple and affordable.

A fast system/apps drive does not really have many benefits, so a partitioned single drive might be quite fast enough for you.

[Umbongo]

I hope I'm not coming across as being argumentative. You guys clearly know a lot on this topic, and I don't. I'm just trying to arrive at an understanding and have yet to see how my proposal is statistically more prone to failure. Any further input is greatly appreciated.

-J

The big difference between your method and a 4 drive RAID 10 setup is that yours will be backed up and a RAID 10 would provide mirroring.

A drive failure on your "data" stripe would mean all changes would be lost, any new files created etc. since the last time machine backup. With mirroring there is an exact copy at all times.

[NoNameBrand]

Your suggestion would be great, except that Drive1 and Drive2 striped = 2TB, so unless I stripe the 2nd set of drives, I'm looking at trying to backup a 2TB volume with a single TB drive/volume.

Partition your drives first, then stripe the partitions.

1TB system volume = 2x500GB partitions. Clone this onto drive three. Back it up to Time Machine on drive four. Use your two free 500GB partitions for other stuff.

I have a five disk setup on my G5 (two internal, three eSATA). For performance, my Photoshop scratch disk is a 32GB four disk stripped array. Each component is a 8GB partition off four of the five disks. Of course I would have better performance with dedicated drives, but this wastes much less space and is still very fast.

My MacPro setup is likely to be similar.

[NoNameBrand]

With mirroring there is an exact copy at all times.

Including file corruption. Always have a backup.

Personally, I'd rather have backup than mirroring.

[jasone6]

Including file corruption. Always have a backup.

Personally, I'd rather have backup than mirroring.

That's been my thinking as well.

[Horst]

Including file corruption. Always have a backup.

Personally, I'd rather have backup than mirroring.

Good point; ideally, one has both, but I'd also rather have a several-hours to 1 day window w/o complete backups than a complete mess due to corruption.

Oh, and make sure to check out this website (http://macperformanceguide.com/) .

[mvasilakis]

Wow thanks for starting this thread. I'm planning something similar.

Only I was planning on striping 4 drives internal and then using an eSATA enclosure externally to back up to 4 separate 1TB drives.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817332013&Tpk=t4s

(Backups don't need to be as fast as the system drives for me so I have no intention of RAIDing any of them.)

After reading through this though I think I will wait for Snow Leopard and see what Z Raids look like. I am waiting for the new Mac Pro's anyway so it looks that that will all happen around the same time.

Thanks for the in depth responses to jasone6's question.

[sidewinder]

Including file corruption. Always have a backup.

Personally, I'd rather have backup than mirroring.
I wouldn't stripe without mirroring and I wouldn't do anything without a backup....

S-

[BobF4321]

The main problem I see is that if disk 3 or disk 4 has a hardware failure then you lose both your system and your Time Machine backup (stripes require all members to be available). The disk 3/4 stripe array should be dedicated to Time Machine. This means the disk 1/2 stripe array should contain system+scratch+userdata. There is little advantage to having separate system and scratch partitions on the same disk performance-wise, and Time Machine excludes scratch files by default. I would make the disk 1/2 stripe array one large partition. Another factor is that journaling is the default these days, so a system crash will VERY rarely corrupt a disk partition.

There is one disadvantage to having a single huge disk partition which I recently discovered when I tried to copy my 1TB Time Machine disk. The directory information was larger than 4GB, which means that all disk copy utilities I tried could not copy it because they are 32-bit applications, which are limited to 4GB of virtual memory. Right now this should only be a problem on the Time Machine disk because it has many copies of the directory structure. If you anticipate having a LOT of files and/or directories it would be safer to have two partitions on the disk 1/2 stripe array: system+ scratch, and userdata.

[jasone6]

The main problem I see is that if disk 3 or disk 4 has a hardware failure then you lose both your system and your Time Machine backup (stripes require all members to be available). The disk 3/4 stripe array should be dedicated to Time Machine. This means the disk 1/2 stripe array should contain system+scratch+userdata. There is little advantage to having separate system and scratch partitions on the same disk performance-wise, and Time Machine excludes scratch files by default. I would make the disk 1/2 stripe array one large partition. Another factor is that journaling is the default these days, so a system crash will VERY rarely corrupt a disk partition.

There is one disadvantage to having a single huge disk partition which I recently discovered when I tried to copy my 1TB Time Machine disk. The directory information was larger than 4GB, which means that all disk copy utilities I tried could not copy it because they are 32-bit applications, which are limited to 4GB of virtual memory. Right now this should only be a problem on the Time Machine disk because it has many copies of the directory structure. If you anticipate having a LOT of files and/or directories it would be safer to have two partitions on the disk 1/2 stripe array: system+ scratch, and userdata.

Thanks Bob... I see your point re: Time Machine and system being on the same disk. I hadn't thought of that before... and in fact, I was trying to keep system and data separate per the research I'd done over at macperformanceguide.com.

Let me just see if I understand you correctly:

- disk 1+2 would be a striped RAID (RAID 0), configured as a single, two-terabyte partition. I'd have scratch, system, and data on this 2-disk volume.
- disk 3+4 would be a striped RAID (RAID 0), configured as a single, two-terabyte partition. This 2-disk volume would be used for Time Machine.

Is that what you're saying? If so, don't you think there'd be an advantage to making a 2nd partition on the disk 1+2 volume? In other words:

Disk 1+2 would have a 64 GIG partition for "scratch" space (utilizing the outside of the disks)
Disk 1+2 would have a second partition (~2tb which would include both the system and data).
Disk 3+4 would be a single partition set as a Time Machine backup for the system/data partition of drives 1+2

The reason I ask is that I know I want the "scratch" space to utilize the absolute fastest part of my disks (again, per macperformanceguide.com ).

Thanks for all the input!

-J

[BobF4321]

The reason I ask is that I know I want the "scratch" space to utilize the absolute fastest part of my disks (again, per macperformanceguide.com ).
-J

I guess the performance benefit really depends on what kind of files will be on the scratch partition. And note that any activity on the system partition will drag the access arm away from the scratch partition. Another consideration is that some day you might run out of scratch space (eg. doing a huge sort or working with HD video), whereas with a single partition all free space is available as scratch.

Are you planning on running Windows in Boot Camp in the future? FYI, Boot Camp doesn't support RAID configurations:
http://support.apple.com/kb/HT2855
(but you could run Windows under VMWare Fusion without Boot Camp)

[Horst]

I wouldn't stripe without mirroring and I wouldn't do anything without a backup....

S-

I wouldn't mirror a stripe, but neither would I use it as storage or backup ;) .

It really depends on how someone wants to use his computer; for me , everything internal is just for system, apps (1 drive), and then performance (all other drives, scratch and temporary data in Raid0).

Data libraries and backups, external drives only.

As my temporary work files/folders are fairly small (6-12GB), I can easily copy them to a different drive while I'm working when needed, without having mirroring slowing me down.
Needless to say, Time Machine is off at all times, only used manually in combination with SuperDuper , and the scratch and data Raid is not being indexed.

Imho, if you want super safe and fast, you have to set up some elaborate and costly external Raid.

[sidewinder]

I wouldn't mirror a stripe, but neither would I use it as storage or backup ;) .
Horst,

I am talking about software RAID here because that is the only option the OP is willing to pursue at this point.

So RAID 1+0 (striping a mirror) is better than RAID 0 from a data security standpoint and better than RAID 1 from a performance standpoint. I would never use any setup, RAID or not, without some kind of backup which is why I suggested RAID 1+0 with Time Machine as ideal. That solution gives you improved performance, data security, higher availability in the event of disk problems, and access to files previously deleted files. All without costing an arm and three legs.

S-

[Horst]

Horst,

I am talking about software RAID here because that is the only option the OP is willing to pursue at this point.

So RAID 1+0 (striping a mirror) is better than RAID 0 from a data security standpoint and better than RAID 1 from a performance standpoint. I would never use any setup, RAID or not, without some kind of backup which is why I suggested RAID 1+0 with Time Machine as ideal. That solution gives you improved performance, data security, higher availability in the event of disk problems, and access to files previously deleted files. All without costing an arm and three legs.

S-

I know what you mean, and agree ; my point is, you can't have it all when you are using internal drives only.
Speed or safety - pick one.

External HDDs are so cheap these days, it seems foolish to store non-essential files on internal drives - all in my humble opinion.

As for Time Machine : it's ok for system backups, and user folders, but that's about it. Even then, it's only good for basic restoring , on the very rare occasion one needs to go back in time to fix a messed up system.

It's a little bit like iLife - bloated, useless, low-quality, and you don't even have to train that monkey to use it ;) .

[sidewinder]

As for Time Machine : it's ok for system backups, and user folders, but that's about it. Even then, it's only good for basic restoring , on the very rare occasion one needs to go back in time to fix a messed up system.

It's a little bit like iLife - bloated, useless, low-quality, and you don't even have to train that monkey to use it ;) .
Horst,

That's being a little hard on Time Machine, isn't it?

Having been bitten by backup software that didn't actually restore when I needed it, I ALWAYS test the restore function of backup software before I consider trusting it.

I installed Mac OS X 10.5 on a disk and enabled Time Machine to back it up. After it was done, I created some test files and let Time Machine back them up. I then let it install all the updates to take it to 10.5.6. Then I took the system disk out of my Mac Pro and stuck a new drive in its place. I booted the Mac OS X 10.5 installer disc and selected the "Restore System From Backup" option and pointed it to my Time Machine volume.

My system was restored with all test files in place. Everything worked as expected.

My point? Time Machine works for full system restores and for going back in time to find files you deleted. And it does all of this simply and without any training. Anyone can use Time Machine which is way more than half the battle. Based on what I have experienced in the Windows world, Time Machine is a phenomenal product and is all 95% of the users need.

S-

[Horst]

Horst,

That's being a little hard on Time Machine, isn't it?

Having been bitten by backup software that didn't actually restore when I needed it, I ALWAYS test the restore function of backup software before I consider trusting it.

S-

Of course you need to make sure a backup software works before relying on it.
I don't think there is one I didn't try, and SuperDuper turned out to be perfect for me, being both easy and reliable .
Time Machine is not a backup solution in my book, just some tacky restore aid .
Being a default feature of Leopard, lacking proper customization tools, I'd actually call it bloatware .

Based on what I have experienced in the Windows world, Time Machine is a phenomenal product and is all 95% of the users need.


I believe 95% of the users don't back up at all.
The remaining 4.5% using TM are posting here asking what 200TB drives to buy or how on earth to retrieve a file from their TM 'backup' . ;)

[sidewinder]

Time Machine is not a backup solution in my book, just some tacky restore aid .
Being a default feature of Leopard, lacking proper customization tools, I'd actually call it bloatware
Horst,

I can't agree with that on several levels.

While Time Machine does not offer much in the way of customization, it does do a very good job of backing up a system. As I am sure you are aware, it does this in two ways. The first, it allows you to restore files that you have deleted or modified by accident or on purpose. It does this amazingly well with an incredibly easy to use user interface. Second, it provides a restore mechanism that can be used to restore what you had in case of drive failure. This is a simple process using the install discs that come with the system.

Does it give the flexibility that True Image does on Windows or Amanda on Unix? No it does not. But that is not the intended market for the software. Time Machine is the first backup software that the masses are likely to use and get some benefit.

I have used True Image and Amanda for years. I'll be honest, I find Time Machine refreshing simple to use and it does what I need for backups on my system. I don't have to think about it. It just does its thing and simply works.

S-

[n8236]

Ez...

Use three hds as raid 5 and the last hd as hot swap. U get parity, redundancy and speed. What more can u ask for.

[sidewinder]

Ez...

Use three hds as raid 5 and the last hd as hot swap. U get parity, redundancy and speed. What more can u ask for.
n8236,

First of all, you can't do RAID 5 without a RAID card which the OP does not have. Second, RAID 5 is still not a substitute for having actual backups. So you need either Time Machine or Time Machine in conjunction with SuperDuper!.

S-

[nanofrog]

Ez...

Use three hds as raid 5 and the last hd as hot swap. U get parity, redundancy and speed. What more can u ask for.
Using hardware RAID, yes. ;)

But the OP gave the impression of using the Mac Pro's software RAID functionality, so no RAID 5 capability. :(

[n8236]

Get a Raid card, yes plz. And yes, plz do SuperDuper along w/ Time Capsule. Then u're pretty much covered. I didn't read the backup portion.

[PowerPaw]

Its interesting that you have presented the solution without the requirements - what are your requirements; these appear to be governed around performance and speed within a tight budget. Is this a correct assumption?

Your best performance gain without going into software RAID 0 :eek: proprietary RAID cards or the expensive one from Apple would be a 300GB backplane version of the WD VelociRaptor drive for your apps and system. SSDs are still a bit expensive, small, new and vary greatly among vendors in performance and technology - there still isn't enough data for reliability.

WD just came out with a 2TB (Green) drive that would suit your requirement for Time Machine - does this really need super performance? For your remaining two bays you can go with RAID 0 for data (these could be smaller cheaper 500GB or 750GB drives too) and rely on your backup and Time Machine or just simply go with a WD Black or the Samsung you mention. In addition to the single data drive option you could put in another performance VelociRaptor for scratch if that is what you are after.

[Aea]

Somewhat agreeing with the above poster.

I would RAID 0 two Raptors, then have the Time Machine on a separate RAID 1 array of 1-2TB drives.

[jasone6]

My requirements are storage, then speed, then reliability.

As I mentioned, I have most of my important files backed up to one or more of several places (online, CDs/DVDs, external HD, etc.). I already own four 1-terabyte hard drives (all 7200 RPM), and I don't want to buy anything else.

I've made a decision, though I'm not done executing it, so I suppose I could still modify my plan:

- I made a 128 GIG partition on one of the drives (#3) and installed a fresh system on it.
- I took the remainder of that drive and striped it with a full-capacity drive (#4) and will use that volume for Time Machine.
- Once I've backed up all my data on my 2 existing drives, I will wipe those, partition a 32 GIG section on each, and stripe those partitions together for a 64 GIG "scratch" partition
- I'll then partition the remainder of those drives together for my main "data" volume.

That leaves me with 4 volumes:
- "scratch" (striped RAID across drives 1 & 2)
- "data" (striped RAID using the remainder of drives 1 & 2)
- "system (single volume on drive 3)
- "Time Machine" (striped RAID across drives 3 & 4)

If drives 1 and/or 2 fails -- I can replace the drive(s), re-stripe and then restore from TM
If drive 3 fails, I'll have to replace it, install a new system, and rebuild TM
If drive 4 fails, I can replace it re-stripe it with the big partition on #3 and re-build TM.

If drive 1 or 2 fails AND drive 3 or 4 fails, well -- that would suck, but like I said, I've got most of my stuff backed up elsewhere anyway.
If 3 or more drives fail, it's likely because the US has sustained an EMP from a nuke detonating in the upper atmosphere, and at that point, my iTunes library will be fairly low on my list of concerns.

-J

[nanofrog]

My requirements are storage, then speed, then reliability.

As I mentioned, I have most of my important files backed up to one or more of several places (online, CDs/DVDs, external HD, etc.). I already own four 1-terabyte hard drives (all 7200 RPM), and I don't want to buy anything else.

I've made a decision, though I'm not done executing it, so I suppose I could still modify my plan:

- I made a 128 GIG partition on one of the drives (#3) and installed a fresh system on it.
- I took the remainder of that drive and striped it with a full-capacity drive (#4) and will use that volume for Time Machine.
- Once I've backed up all my data on my 2 existing drives, I will wipe those, partition a 32 GIG section on each, and stripe those partitions together for a 64 GIG "scratch" partition
- I'll then partition the remainder of those drives together for my main "data" volume.

That leaves me with 4 volumes:
- "scratch" (striped RAID across drives 1 & 2)
- "data" (striped RAID using the remainder of drives 1 & 2)
- "system (single volume on drive 3)
- "Time Machine" (striped RAID across drives 3 & 4)

If drives 1 and/or 2 fails -- I can replace the drive(s), re-stripe and then restore from TM
If drive 3 fails, I'll have to replace it, install a new system, and rebuild TM
If drive 4 fails, I can replace it re-stripe it with the big partition on #3 and re-build TM.

If drive 1 or 2 fails AND drive 3 or 4 fails, well -- that would suck, but like I said, I've got most of my stuff backed up elsewhere anyway.
If 3 or more drives fail, it's likely because the US has sustained an EMP from a nuke detonating in the upper atmosphere, and at that point, my iTunes library will be fairly low on my list of concerns.

-J

I take it you like living dangerously when it comes to your data. :eek: :p

I see a problem with drives 3 & 4. The partitions must be the same size, if not using the entire drive when creating a strip. To balance it, what ever the size of the OS partition, you'd have to do the same with drive 4. Then stripe the two remaining pieces of both drives. Otherwise, you get wasted space. (It's always based on the smallest component, whether it be a partition, or the entire drive).

You'd be better off rethinking this I think. Separate as much as you can. For example, your setup of drives 1 and 2, put high usage on it 2x, as it's handling data and scratch files.

I think you'd be safer to just split it into (non RAID):
drive 1 = OS
drive 2 = Scratch
drive 3 = Data
drive 4 = Time Machine

The load would be split among completely separate drives, so you would get a higher throughput. :)

Beyond that, you get into RAID. :eek: Consumer drives aren't really up to the task, as their unrecoverable bit error is a little low for such usage. :(
If you do decide to go this route, and use the existing equipment, you might want to re-examine the RAID 1+0 suggestion. The MP is capable of this via software RAID. Better than RAID 0 any day, as you have some redundancy, and still get a speed boost. Anything else would require a RAID card, bare minimum, keep spares on hand, and switch to enterprise drives. It might seem obsessive, and over blown, but it's the result of experience.

[dabirdwell]

Wow thanks for starting this thread. I'm planning something similar.

Only I was planning on striping 4 drives internal and then using an eSATA enclosure externally to back up to 4 separate 1TB drives.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817332013&Tpk=t4s

(Backups don't need to be as fast as the system drives for me so I have no intention of RAIDing any of them.)

After reading through this though I think I will wait for Snow Leopard and see what Z Raids look like. I am waiting for the new Mac Pro's anyway so it looks that that will all happen around the same time.

Thanks for the in depth responses to jasone6's question.


I appreciate a little more discussion on plausible internal RAID solutions for the MP. I started a similar thread recently and am still trying to learn as much as possible while I wait for Gainestown.

I am, however, going to latch onto something here that may be a bit peripheral- ZFS. A couple of posters have mentioned it in relation to Snow Leopard, but this is the first I've heard of it in probably a year or more. Last I heard, there was no reason to believe it had become bootable with OSX.

Of course, in the back of my mind, I've been wondering if they had made it work and would introduce it in SL; but has anybody seen evidence of this, or is this mostly educated speculation? I'd love to believe that we might have ZFS-based Snow Leopard running on Gainestown chips this year, including self-healing expandable storage pools and efficient system snapshots.

[nanofrog]

I appreciate a little more discussion on plausible internal RAID solutions for the MP. I started a similar thread recently and am still trying to learn as much as possible while I wait for Gainestown.

I am, however, going to latch onto something here that may be a bit peripheral- ZFS. A couple of posters have mentioned it in relation to Snow Leopard, but this is the first I've heard of it in probably a year or more. Last I heard, there was no reason to believe it had become bootable with OSX.

Of course, in the back of my mind, I've been wondering if they had made it work and would introduce it in SL; but has anybody seen evidence of this, or is this mostly educated speculation? I'd love to believe that we might have ZFS-based Snow Leopard running on Gainestown chips this year, including self-healing expandable storage pools and efficient system snapshots.
The last I saw, ZFS is slated for the Server edition of Snow Leopard, not the Client edition. It would be placed into the client edition at a later date, either as an update, or not until 10.7. (Personally, I lean towards the latter, as updates gives them time to work out whatever issues it might have). ;)

[rylin]

The last I saw, ZFS is slated for the Server edition of Snow Leopard, not the Client edition. It would be placed into the client edition at a later date, either as an update, or not until 10.7. (Personally, I lean towards the latter, as updates gives them time to work out whatever issues it might have). ;)

I'd actually say as a client download.
I wouldn't be the least bit surprised to see a stable version of ZFS available on macosforge (edit:) when Snow Kitteh is launched.
Not advertised by Apple, of course, but there for those of us who know what we want and will use and recommend FAT32 if we can't get it! ;)

[nanofrog]

I'd actually say as a client download.
I wouldn't be the least bit surprised to see a stable version of ZFS available on macosforge (edit:) when Snow Kitteh is launched.
Not advertised by Apple, of course, but there for those of us who know what we want and will use and recommend FAT32 if we can't get it! ;)
Mmm... That would be nice! :D :D