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Raid 0 (Striping) on the new Mac Mini Server

Serif

Serif

macrumors regular
Original poster
Jul 10, 2008
139
17
UK
I'm looking at getting one of the new Mac Mini servers to play with at home and would like to set it up to use RAID 0 to try and get better performance out of the 5400 disks. I have a couple of questions.

Can anyone give me an estimate of percentage speed up for reads and writes over a RAID 1 and/or using the two disks without RAID?

How are the disks configured when the unit is shipped? To use RAID 0 will I have to reformat and reinstall, presumably using media mounted on another Mac with an optical drive?

Thanks for any help with this.
 
Funny you should mention it, my new mac mini arrived a couple of hours ago, and I'm in the process of doing exactly that.

The disks are configured as two separate volumes when they arrive - "Server HD" and "Macintosh HD2" - there's no option to configure raid during set-up (which I feel is a missed opportunity by apple).

I created a degraded raid array using the "Macintosh HD2" disk and cloned it from the "Server HD" volume. Then I rebooted on to the degraded array, unmounted the original disk, and added it to the raid set. This works (to an extent), but the later disk I added to the array is degraded. I'm in the process of trying to rebuild it after repairing permissions (there were a lot of permissions that needed repairing).

I'll let you know in a few minutes how it turns out.
 
Since the hard drives are preconfigured. You would need to boot up with the restore/install DVD and start from scratch, run Disk Utility and setup the Stripe set there. Then install OS X server.

I wouldn't suggest doing what the poster above did.
 
calderone said:
I wouldn't suggest doing what the poster above did.
Click to expand...

I agree, as a degraded RAID 0 array means all data is lost and you'll need to do a restore. You cannot create a degraded RAID 0 array that I'm aware of, and I'm not sure why anyone would want to.
 
Apologies, I saw the RAID1 in the original text, and jumped the gun: Of course, I am talking about RAID 1 not RAID 0.

I would certainly wait to see if it works - for myself, I figured that if I would have to reformat the whole thing to get raid0 anyway, it was worth trying out for curiosity's sake.
 
yamahito said:
Apologies, I saw the RAID1 in the original text, and jumped the gun: Of course, I am talking about RAID 1 not RAID 0.

I would certainly wait to see if it works - for myself, I figured that if I would have to reformat the whole thing to get raid0 anyway, it was worth trying out for curiosity's sake.
Click to expand...

Keep me/us posted re RAID 1 on the Mac Mini Server. I'm in the same boat. Not sure how valuable it will be, as I will likely have my data in an external RAID array and my O.S. disk will be pretty static. But if the two internal disks can easily be setup as a mirrored RAID pair, I might go that route.
 
MacToddB said:
Keep me/us posted re RAID 1 on the Mac Mini Server. I'm in the same boat. Not sure how valuable it will be, as I will likely have my data in an external RAID array and my O.S. disk will be pretty static. But if the two internal disks can easily be setup as a mirrored RAID pair, I might go that route.
Click to expand...

FYI, I got RAID 1 working on my Mac Mini Server WITHOUT REINSTALLING or even touching the DVD.

Details here:

https://forums.macrumors.com/showthread.php?p=8705018
 
Cool: well done.

I gave up and reinstalled in the end: I'm not sure that it would have been any more hassle than the super duper route, to be honest!

Ah well, here's to curiosity!

T
 
Thanks for the replies. I'm curious if there is any noticeable slow down for disk access once it is in mirroring (RAID 1) configuration? Part of the reason for being interested in configuring for RAID 0 is to try and get some improved performance out of disk accesses and I'd rather not go down the route of swapping in 7200 disks both for reasons of cost and because they may run hotter.
 
I'm not really intending to do any speed tests: for me, raid is about resilience rather than speed.

General rule of thumb is that raid1 is slightly faster for reads, slower for writes. I can't say that it's really noticeable for my purposes.

Why is disk access speed important to you?
 
yamahito said:
Why is disk access speed important to you?
Click to expand...

Well it's not really that important since I'll be using the mini server with a firewire connected backend disk array running as RAID 5. That's where my backups will be and takes care of the resilience. If I was running RAID 1 and one of the internal disks went I'd still end up opening the box so I figured I may as well stripe them and see if I could get some speed up accessing my applications and system files. I'm just curious if this will gain me much.
 
The worst bottleneck of a computer nowadays is still the hard drive, disproportionately more horrid performance-wise than just about every other computer component - so the answer to 'Why is disk access speed important to you' should be obvious, the question is almost ridiculous. With Raid0, random access is still the same speed but sustained read and write speed improve up to 2x (for 2 drives, Nx for N drives). With Raid1, since both drives are each writing a copy of the same bits there is no improvement in write but sustained read speed improves up to 2x (for 2 drives, Nx for N drives) but not quite as good as Raid0 because of the mirroring overhead (overhead between mirroring and striping is different but I'm not sure by how much).

So if you want a faster hard drive either buy a faster hard drive or take the hard drives you have and hook them up together in Raid0. If you are simply worried about losing data, either backup on a regular basis or do Raid1. If you want the best of both worlds, I would rather recommend Raid5 instead of a combination of Raid0 and Raid1. Raid5 has the best combination of speed improvement versus added redundancy, but you need at least 3 drives for Raid5, and not all raid controllers support Raid5.
 
I agree with the raid 5, kind of like the lime-technologies UnRaid format,

it is pretty freaking cool, it may work for the mac, but not sure?

it is pretty nice,

if someone sets one up let us know, it runs a parody drive so if some drive fails, then it wont be lost.

looks good...
 
j2048b said:
if someone sets one up let us know, it runs a parody drive so if some drive fails, then it wont be lost.
Click to expand...

I think you mean "parity" not parody. i.e. an extra drive (or stripe) that contains a checksum of the data on the other drive (or stripes)

CodeJingle said:
With Raid1, since both drives are each writing a copy of the same bits there is no improvement in write but sustained read speed improves up to 2x...
Click to expand...

This is true IF THE DRIVES ARE ON SEPARATE CONTROLLERS. Since this does not appear to be the case with the Mac Mini, I'm worried that the Write Speed could approach 0.5x, since the info has to be written twice on the same channel before the write is considered complete. I am noticing some sluggishness with my Mac Mini Server running RAID 1 mirrored internal 500GB disks, and I might break the RAID and see if things improve. Anyone else in the same boat?


If you want the best of both worlds, I would rather recommend Raid5 instead of a combination of Raid0 and Raid1. Raid5 has the best combination of speed improvement versus added redundancy, but you need at least 3 drives for Raid5, and not all raid controllers support Raid5.
Click to expand...

RAID 5 does not have the best combination of redundancy. If 2 disks fail in RAID 5, you're out of luck. But with RAID 1+0, depending on which disks fail, you can theoretically survive up to N disk failures in a 2N configuration.
RAID 5 is for performance with a some inherent redundancy. RAID 1+0 provides both performance and higher redundancy.

http://en.wikipedia.org/wiki/RAID
 
For those that already have a Mac Mini Server, I'm curious if anyone has an external DVD hooked up to it. If so, is it possible to watch a DVD and would iDVD work on the external? Does the external need to be a MacBook Air SuperDrive for this to work - or would any external dvd drive work?

I noticed yamahito mentioned that he re-installed, and was wondering if it was from an external DVD...

Sorry to hijack the thread, but I haven't seen many who have purchased the Mini Server yet. I'm hoping to get one soon, and plan on using it as a multipurpose machine (test server that can also be used as a desktop), which is why I am wondering how SL Server views external DVD burners. I know in the past OS X was not very happy with external burners, and was wondering if this might still be the case?
 
Bandwidth used for IO for a single hard drive does not use up all the bandwidth of a single controller. Bandwidth is shared by all channels at any given time, and any recent controller supports simultaneous IO on all channels, and total bandwidth is limited by the controller's bandwidth (the different drives are on the same controller but not the same channel, I don't think your statement is accurate that the drives are on the same channel or I guess I am saying you are wrong on that count). SATA 3 gb/s - 3 gigabits/sec - is ~375 megabytes per second, you don't think one SATA drive uses up ~375 megabytes/sec of bandwidth? No, so 2 drives in Raid0 will increase your sustained read and write up to 2x, and would never decrease the speed. Can make a bet on it if u think otherwise, I'm thinking of getting a mac mini server myself.

Right well if both sides of a mirror fail then that is just as bad, unless you are mirroring twice. Plus that Wikipedia article needs cites for verification. I myself would prefer to maximize speed but still have a minimum of redundancy, that is pretty much what Raid5 is for. And unless more than one drive fails in an instantanous fashion, the requirements of Raid5 should be fine for most purposes. As long as the expected time between drive failures is size-ably longer than the expected time to find a drive failure, replace the drive, and for the Raid5 array to rebuild the lost drive.
 
CodeJingle said:
Bandwidth used for IO for a single hard drive does not use up all the bandwidth of a single controller. Bandwidth is shared by all channels at any given time, and any recent controller supports simultaneous IO on all channels, and total bandwidth is limited by the controller's bandwidth (the different drives are on the same controller but not the same channel, I don't think your statement is accurate that the drives are on the same channel or I guess I am saying you are wrong on that count). SATA 3 gb/s - 3 gigabits/sec - is ~375 megabytes per second, you don't think one SATA drive uses up ~375 megabytes/sec of bandwidth? No, so 2 drives in Raid0 will increase your sustained read and write up to 2x, and would never decrease the speed. Can make a bet on it if u think otherwise, I'm thinking of getting a mac mini server myself.
Click to expand...

If you re-read my post, I was talking about RAID 1, i.e. MIRRORING!

Writing the SAME DATA TWICE (RAID 1) uses more bandwidth, plain and simple. Now, if you think the bus on the Mac Mini makes the extra delay negligible, that's possible, but it's obviously not zero and certainly not faster for writes. It appears you were reading something other than what I wrote.

Right well if both sides of a mirror fail then that is just as bad, unless you are mirroring twice. Plus that Wikipedia article needs cites for verification.
Click to expand...

It's still correct. Pick another source:

http://www.devhardware.com/c/a/Opinions/Western-Digital-Raptors-versus-RAID-Arrays/

"If the user is able to shell out a bit more, then RAID 1+0 (or 0+1) is unquestionably the best option. That is because you benefit from the best of both worlds. It's like picking out the pros from both. The only downside to this is that it requires four disks."


I myself would prefer to maximize speed but still have a minimum of redundancy, that is pretty much what Raid5 is for.
Click to expand...

Right. Not "BEST" of both worlds, but best performance, with passable redundancy.

And unless more than one drive fails in an instantanous fashion, the requirements of Raid5 should be fine for most purposes. As long as the expected time between drive failures is size-ably longer than the expected time to find a drive failure, replace the drive, and for the Raid5 array to rebuild the lost drive.
Click to expand...

Which is hardly "instantaneous".

CodeJingle said:
So if you want a faster hard drive either buy a faster hard drive or take the hard drives you have and hook them up together in Raid0. If you are simply worried about losing data, either backup on a regular basis or do Raid1. If you want the best of both worlds, I would rather recommend Raid5 instead of a combination of Raid0 and Raid1.
Click to expand...

There's that phrase again. RAID 5 is not the "best of both worlds" if the "worlds" are performance and redundancy. It's reasonable to recommend RAID 5 if price is one of those worlds, but RAID 1+0 is the best of both worlds.
 
noob here - I just followed some excellent instructions from this thread, but don't see the post anymore. Too bad since I didn't save the instructions. Am I doing something wrong that I can't see the post anymore?

Anyway, the trick was to start the graphical disk utility in debug mode so the Lion boot partition could be shown - and then copied to a USB stick.

I booted from the USB, set up RAID 0 and recovered from a Time Machine backup. Took about 2 hours to restore 100GB, then it rebooted and works great so far, it really does go faster.

Thanks.
 
metd01567 said:
noob here - I just followed some excellent instructions from this thread, but don't see the post anymore. Too bad since I didn't save the instructions. Am I doing something wrong that I can't see the post anymore?

Anyway, the trick was to start the graphical disk utility in debug mode so the Lion boot partition could be shown - and then copied to a USB stick.

I booted from the USB, set up RAID 0 and recovered from a Time Machine backup. Took about 2 hours to restore 100GB, then it rebooted and works great so far, it really does go faster.

Thanks.
Click to expand...

Thanks, sounds like you did it right. I posted my answer on this thread, ~2 years ago, and yesterday replaced that Mac mini server with a new Lion version, with SSD hard drive! Very cool little server!
 
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