Stardom's Pro Drive and RAID 1

[NoManIsland]

This may be somewhat of a foolish question, but I read that Stardom/Trans International's Pro Drive (http://www.raidon-usa.com/stardom/pro_drive_feature.html) uses port multiplication technology to provide a RAID pair of 2.5" drives in each HDD bay of a Mac Pro, so using its hardware RAID 0 bottlenecks because of the halved bandwidth. My question is, if its RAID 1 setting is used instead, will it still halve the performance? I love the idea of the tech, so I almost want to find a way to work it into my setup, and having each bay with a mirrored pair would be really cool Also, since the RAID pairs would present as normal drives, could I then put them in a software or hardware RAID 0, and would this bottleneck in some way?

 

[NoManIsland]

Nanofrog, I'd love your input on this one

 

[Loa]

Hello,

I can't answer your question as it's just a bit over my technical knowledge, but I'm always curious when people use RAID1 for a non-server, non-critical setting.

Would you mind taking 2 minutes to tell me why you want/need RAID1?

Thanks

Loa

 

[NoManIsland]

Hello Loa,

I'm a classical composer and I had a very bad HDD death years ago that took almost 6 years of my music with it, as a new disk died in the 1 hour window while I was transferring files. Because of this, I do my best to have double redundancy, combining RAID 1 with Time Machine. In this case I was specifically looking for RAID 1 for my boot drive, so that I can continue working if the drive fails, as I use my computer for my business as well as my music, and downtime could represent a major issue on that front.

 

[nanofrog]

Nanofrog, I'd love your input on this one

So you do want to use a Pro Drive with a RAID 1 set of SSD's.

I gave you an answer in the other thread you posted in.

 

[jonatraidon-usa]

RAIDON/STARDOM Pro Drive for Mac Pro machines, 2 models

We actually have 2 different models, the PD2520 is RAID 0 2 X 2.5" hdd's or SSD & the PD2510 which is hardware RAID 1 2 X 2.5" hdd's or SSD.
Both products work with the latest Mac Pro machines.

The PD2500 was RAID 0 or RAID 1 but did NOT work in Nehalem Mac Pro machines.

The RAID 0 product is fixed, but is portable with FW800 & USB2.0 plugs in the back for use offsite.

The RAID 1 product is also fixed, no FW or USB.

Product page here: http://www.raidon-usa.com/stardom/pro_drive_feature.html

Anything else, drop us a line.

Nanofrog, I was with CalDigit as the Director of Business Development, I left CalDigit in Nov of 09'

Jon

 

[Loa]

Hello,

Sorry for the very late reply; don't know why I missed this.

I'm a classical composer and I had a very bad HDD death years ago that took almost 6 years of my music with it. [...] Because of this, I do my best to have double redundancy, combining RAID 1 with Time Machine.

You almost lost your data because you lacked a back-up, not redundancy.

As you allude to further on, back-ups and drive redundancy are not the same thing. People use RAID1 (or other redundancy RAID types) as protection against down-time rather than protection. If what you need is data protection, what you need is a back-up plan (that doesn't involve redundancy).

RAID1 and Time Machine cannot be considered double redundancy in the strict sense of the word "redundancy" in a RAID1 context.

If money is tight, I'd invest in a second, off-site back-up drive instead of a RAID1 set-up. Of course, if it's not an issue, why not get both?

Good luck,

Loa

 

[Apple Corps]

Loa back-up or redundancy

Semantics or not?

If I use a mirrored raid setting I am backing up to an external disk that creates a second "backup" on the mirrored drive. My boot & apps are in drive bay #1 - my libraries / data are going into an external enclosure set to mirror 2 drives.

Short of off site storage I am backed up or redundant - am I not?

 

[nanofrog]

Nanofrog, I was with CalDigit as the Director of Business Development, I left CalDigit in Nov of 09'

Nice to hear from you.

I do recall my phone calls with you, which were courteous and professional.

My issues with the product were purely technical, and as it went on, left me with the overwhelming impression that the product was too immature at the time of release. I presume that the communication issues on product capababilities were between the engineers at CalDigit and the ODM, and that information was passed on to you.

At any rate, I hope you're doing well, and are much happier at RAIDOM.

If I use a mirrored raid setting I am backing up to an external disk that creates a second "backup" on the mirrored drive. My boot & apps are in drive bay #1 - my libraries / data are going into an external enclosure set to mirror 2 drives.

Short of off site storage I am backed up or redundant - am I not?

RAID /= Backup

For example, if you accidentally erase a file, it's repeated on the mirror. Without a backup, that file is gone. User error is a major reason to have a backup, single disk or RAID.

There's also hardware failures to consider. For example, disks may not survive certain catastrophes such as the PSU fries and takes out ALL the disks at once.

Off site backups are for another type of catastrophe, which are Acts of God (fire, flood,...).

Hope this helps clear things up.

 

[Apple Corps]

nano - got that - if the main concern is drive failure, than mirror raid meets the need (I think)

Time machine would protect against user erase error as well. As my data is external I guess I could use time machine to external drive X and mirror that.

This is very timely for me as I am in the process of configuring my external storage system. With 1080p HD all of the time machine backup and mirror raid start to require a lot of storage

 

[nanofrog]

nano - got that - if the main concern is drive failure, than mirror raid meets the need (I think)

Yes, this is the case.

A mirror is typically used for the OS in servers, as it's a means of keeping the system running 24/7, as it does allow for a disk failure without needing to shut down, repair, and bring the system back online. But it's useful in any system where the data needs to be available for 24/7 conditions (but if the OS isn't, it's rather useless ), which is why that's it's primary usage.

In RAID speak, Availablility = Uptime.

Time machine would protect against user erase error as well. As my data is external I guess I could use time machine to external drive X and mirror that.

TM is your backup source, so long as you have the drive. But you DO NOT want to mirror it. Backups and RAID aren't mirrored. The "connection" is via software tools that launch an automated backup cycle (full or incremental copy).

That way, if you make a mistake on the mirror, the needed data can be returned to the mirror via the backup source. If you mirror that to a mirror, the mistake is automatically copied by the RAID function. Not good at all.

This is very timely for me as I am in the process of configuring my external storage system. With 1080p HD all of the time machine backup and mirror raid start to require a lot of storage

Just make sure you've adequate capacity for the backup source. With the size of 1080P files, it might be a good idea to look into Port Multiplier enclosures used with an eSATA card that supports PM chips. (You can JBOD multiple disks, as it appears as a single large volume to the system).

It's a way to get a lot of capacity at low cost. The only thing cheaper, is to JBOD internal disks (or stripe, if you don't care about a single disk causing total failure). JBOD only loses the disk that dies (the data on the others in the set remains in tact), and is it's advantage for backup solutions. And as speed is less of a concern, that tends not to be an issue, unless the capacity is extreme, and another RAID would be required (but you still only use backup software, not a mirror).

 

[Apple Corps]

Lets' dive a bit deeper.

If I backup to external drive X, what happens if drive X fails - where is the protection for that?


Next - I'm currently looking at purchasing a Proavio 8 bay edit box SAS/SATA combo. My understanding is that with port multipliers all drives share the 3 Gb/s bandwidth. With a number of the high density 7200 rpm drives now reaching 300Mb/s (at least on the outer tracks) one could easily exceed 3 Gb/s. Clearly though, either mini SAS or a port multiplier will be necessary - no way 8 cables are headed into the Mac Pro. What is the computer bandwidth if m host controller goes into a 4x slot under SATA 2.0?

 

[Apple Corps]

Wow - 4x slot under 2.0 = 2 GB/s in one direction - 4GB/s bidirectional

 

[nanofrog]

Lets' dive a bit deeper.

If I backup to external drive X, what happens if drive X fails - where is the protection for that?

You'd need another disk, and set it as a backup as well. Or use an Off Site source via an ISP connection (provides protection from Act of God issues at the system's location, as well as theft of actual equipment).

You can also create 2x mirrors that are independent of one another in the RAID setup. Then use backup software to perform the automated backups from A to B on whatever schedule you deem fit to fulfill your needs.

Simply put, you can use a RAID to backup another RAID. But there is no connection in the RAID software or on the card if it's a hardware implementation. Each array needs to be separated in the sense of direct connections to prevent previously discussed issues from happening. Backup software isn't direct, it's indirect and only occurs when the scheduled time is reached.

Next - I'm currently looking at purchasing a Proavio 8 bay edit box SAS/SATA combo. My understanding is that with port multipliers all drives share the 3 Gb/s bandwidth. With a number of the high density 7200 rpm drives now reaching 300Mb/s (at least on the outer tracks) one could easily exceed 3 Gb/s. Clearly though, either mini SAS or a port multiplier will be necessary - no way 8 cables are headed into the Mac Pro. What is the computer bandwidth if m host controller goes into a 4x slot under SATA 2.0?

EB8-PM /= EB8-MS.

The first uses a Port Multiplier chip, the second is direct connections via an SFF-8088 connector (external Mini SAS). The latter unit can be used with either a RAID card, or non-RAID Host Bus Adapter (they do exist). Cables are clean, but the performance is generated via a RAID card and using the drives in parallel.

However, I presume you meant the EB8-PM unit, which allows you to connect 1x eSATA port per 4x disks in the enclosure (so to operate all 8bays, you'd need 2x eSATA ports and cables). One card can provide both ports, and very inexpensively as well. PM chips can run up to 5x disks per eSATA port, but you'd need an EB10-PM to do that (or equivalent from another manufacturer).

What you need to understand with PM chips and throughputs, is that at best (disks are RAID0), each can switch between the disks attached to it to achieve a max of 250MB/s or so (3.0Gb/s spec parts). Double it for 6.0Gb/s parts.

In JBOD, it's only as fast as a single disk. Even if you ran WD RE4's (WD2003FYYS), the avg. throughput is ~109.8MB/s (read and write of a single unit; value obtained from test data available from Tom's Hardware for this drive model). 3.0Gb/s or 6.0Gb/s ports won't make a difference here, as either is more than capable of handling a single mechanical disk. SSD can be another matter however.

As per bandwidth of a 4x lane PCIe slot, it's 4*500MB/s (per lane), = 2GB/s. But you'll never see that in practice with an eSATA card. 1GB/s, maybe, with 10x fast disks in a RAID 0 (based on 100MB/s per disk).

 

[DoFoT9]

In JBOD, it's only as fast as a single disk. Even if you ran WD RE4's (WD2003FYYS), the avg. throughput is ~109.8MB/s (read and write of a single unit; value obtained from test data available from Tom's Hardware for this drive model). 3.0Gb/s or 6.0Gb/s ports won't make a difference here, as either is more than capable of handling a single mechanical disk. SSD can be another matter however.

and the fact that JBOD will only write to disk #2 once disk #1 is full. means that the drives arent evenly worn etc - would not be a great idea for OSs or anything really.

 

[nanofrog]

and the fact that JBOD will only write to disk #2 once disk #1 is full. means that the drives arent evenly worn etc - would not be a great idea for OSs or anything really.

That's why it's single drive operation.

But it is usefull for inexpensive mass storage, such as backup. Such systems aren't meant to be used for high availability environments (primary data source). Power management will spin the drives down when they're not in use, and only spin them up when a backup schedule occurs. And in cases of external enclosures, you may have a power switch that you can use to physically disable it from the system when it's not in use (a mistake IMO however, as it's libel to remain OFF when the next schedule is set to begin). Human error strikes again ...

 

[DoFoT9]

That's why it's single drive operation.

forgive my n00bism.

But it is usefull for inexpensive mass storage, such as backup. Such systems aren't meant to be used for high availability environments (primary data source). Power management will spin the drives down when they're not in use, and only spin them up when a backup schedule occurs. And in cases of external enclosures, you may have a power switch that you can use to physically disable it from the system when it's not in use (a mistake IMO however, as it's libel to remain OFF when the next schedule is set to begin). Human error strikes again ...

LOL. but yes very useful for backups of backups, which could be done weekly/monthly i guess. .

is it more beneficial to keep a hard drive in a powered-ON state (but spun down), or completely off at the power switch?

 

[Apple Corps]

Nano - it is the mini SAS that I'm most leaning towards. Part of the decision process is the 10' - 12' cable run I need to make - I believe that sata maxes at around 6' or so.

SO - lots to consider further. Also - the size of many of my video clips are small - no 145 minute feature films The point being is that fast vs ultra fast will probably only save me a few minutes a day. More and more I am discerning all of this chasing tech specs and trying to view them through the lens of practical day to day performance differences that I will see. I finally had to purchase a new current model MP as work demands are growing. Circumstance demanded the replacement of my MacBook Pro a month or so before the latest version was released - never looked back or had any second thoughts about it.

I may just wind up with a port multiplier sata if I can sort out the cable length.

 

[nanofrog]

Nano - it is the mini SAS that I'm most leaning towards. Part of the decision process is the 10' - 12' cable run I need to make - I believe that sata maxes at around 6' or so.

It will depend on the type of drives used.

SATA has a limit of 1.0m for passive signals, and 2.0m for active signals.

Since a PM chip = active, Yes, you'd have a limit of ~6' with the EB8-PM. Unfortunately, if you went with the EB8-MS, it's passive and you'd be stuck to 1.0m. Unless you used SAS expanders (equivalent of PM chip for SAS connections, and it's capable of handling SATA disks as well).

You'd also need to add in either a SAS HBA (and run SAS disks to exceed 2 meters) or a RAID card, also running SAS disks. An expander would also do it, so base this on cost.

Getting past 2.0 meters is going to up the costs. SAS can go up to 10 meters. But the disks are more expensive for less capacity, and the expander solution isn't exactly cheap either (though there are different disk capability units, and it will affect cost).

SO - lots to consider further. Also - the size of many of my video clips are small - no 145 minute feature films The point being is that fast vs ultra fast will probably only save me a few minutes a day. More and more I am discerning all of this chasing tech specs and trying to view them through the lens of practical day to day performance differences that I will see. I finally had to purchase a new current model MP as work demands are growing. Circumstance demanded the replacement of my MacBook Pro a month or so before the latest version was released - never looked back or had any second thoughts about it.

I may just wind up with a port multiplier sata if I can sort out the cable length.

What exactly do you need to do that will mean long cables?

 

[nanofrog]

SAS HBA's (non RAID):
ATTO ExpressSAS H380
ATTO ExpressSAS H680 (6.0Gb/s version)

Areca ARC-1300ix-16

 

[nanofrog]

forgive my n00bism.

Nothing to forgive. You're understanding of how they're written to is correct. You just didn't put the rest of it together which is the throughput = single disk operation. Easy thing to happen.

I've certainly had my share of "brain farts".

LOL. but yes very useful for backups of backups, which could be done weekly/monthly i guess. .

JBOD is fine for backing up most things (especially home users, SMB, workstation DAS arrays for example), save a few critical uses or where mass storage is so large, JBOD can't complete the task during the nightly run (even if the main storage is actually multiple arrays, where parallelism can work in your favor to meet the schedule time).

is it more beneficial to keep a hard drive in a powered-ON state (but spun down), or completely off at the power switch?

I'd say ON. Startup or resume from sleep will cycle the drives (they can go bad if you don't; just ask those who put drives in closets for safe keeping, and couldn't get them to work a year or two later).

Ideally, it needs to be protected from power issues, including brown-outs (which means plugged into a UPS, not just a surge protector).

If you were to go on vacation (no new data would need to be written for an extended period of time), then shut it OFF until you return.

 

[DoFoT9]

Nothing to forgive. You're understanding of how they're written to is correct. You just didn't put the rest of it together which is the throughput = single disk operation. Easy thing to happen.

I've certainly had my share of "brain farts".

i knew that it could only read at 1x the speed - yea, silly brain farts

JBOD is fine for backing up most things (especially home users, SMB, workstation DAS arrays for example), save a few critical uses or where mass storage is so large, JBOD can't complete the task during the nightly run (even if the main storage is actually multiple arrays, where parallelism can work in your favor to meet the schedule time).

for using as a primary backup of those services you just listed? why would you pick a JBOD over a mirrored software RAID? there arent any cost differences..

I'd say ON. Startup or resume from sleep will cycle the drives (they can go bad if you don't; just ask those who put drives in closets for safe keeping, and couldn't get them to work a year or two later).

Ideally, it needs to be protected from power issues, including brown-outs (which means plugged into a UPS, not just a surge protector).

If you were to go on vacation (no new data would need to be written for an extended period of time), then shut it OFF until you return.

right i wasnt aware of that, i normally leave my external drives in "standby" mode - with the light on i guess that will make them last longer. no UPS though power is generally good.

 

[Loa]

Lets' dive a bit deeper.

If I backup to external drive X, what happens if drive X fails - where is the protection for that?

As Nano said, you need a second external (off-site is better) back-up.

But in reality, you're only screwed if both your main disk and back-up disk fail *at the same time*. Drive failures (not data corruption or accidental deletion, but real drive failures) are pretty rare. The chances that an internal and external drive fail at the same time is pretty slim.

Loa

 

[Apple Corps]

nano - the longer cables are mainly for equipment placement (aesthetics I guess) in my work area. I've been using an Anthro Bench for several years - really love it - but am trying to balance and "clean up" the equipment placement during this upgrade cycle.

BTW - NoManIsland - sorry for highjacking your thread

 

[nanofrog]

for using as a primary backup of those services you just listed? why would you pick a JBOD over a mirrored software RAID? there arent any cost differences..

The reason isn't cost, but maximizing capacity. A mirror only provides the capacity of a single disk (capacity = n/2, or that of the smallest disk, if they're unequal in capacity), while JBOD is the added capacity of every disk in the set (drives don't have to be the same capacity, make or model).

As Nano said, you need a second external (off-site is better) back-up.

But in reality, you're only screwed if both your main disk and back-up disk fail *at the same time*. Drive failures (not data corruption or accidental deletion, but real drive failures) are pretty rare. The chances that an internal and external drive fail at the same time is pretty slim.

Loa

The drives used will make a big difference here. Such as trying to use consumer models for RAID, as they're not built for it.

JBOD has an unusual advantage, as if a disk goes, all the others will still operate, and only the data on the failed disk is gone from the set.

So if you were running the primary array as a stripe set (one disk fails, all data is gone), the entire JBOD would have to fail to reproduce the same event on the backup system. This isn't common, but there is an actual risk (low chance of occurance).

Now if the data is truly critical, an Offsite backup system is something you need to use, no matter how the primary array or primary backup source is configured (onsite).