Mac Pro Upgraded - 3xSSD's in RAID0

[VirtualRain]

Have you had any problems with your Raid setup ?
I had 2 80GB G1's in a Raid 0 and one of my drives died last week! I just can't believe I have that bad of luck...LOL
But, Intel just replaced the dead one with a G2 so I guess i'm lucky there !
I'm not gonna Raid them this time- Gonna put the G1 in my Macbook Pro.

I've had zero issues with my G1's (knock on wood). It sounds like you may have just been unlucky with yours as it would appear to have been a hardware failure. Other's here are having file system issues with the G2 drives in RAID with 10.6.2. So far, it seems the G1's in RAID0 on 10.6.2 are fine. At least my prior array of two drives and this stripe of 3 seem to perform flawlessly.

At any rate, living on the bleeding edge does require a good backup strategy in the event the worst should happen.

 

[playalistic]

Slightly OT I guess, I've just installed 2 x 80GB X25-M G2's in RAID0 but have yet to decide on the block (or properly known as stripe) size. I'm thinking 64k but wondered if the cell size of the Intel drives needs to be considered regarding write amplification etc etc.

 

[robains]

Slightly OT I guess, I've just installed 2 x 80GB X25-M G2's in RAID0 but have yet to decide on the block (or properly known as stripe) size. I'm thinking 64k but wondered if the cell size of the Intel drives needs to be considered regarding write amplification etc etc.

The best answer is you will need to experiment. There are so many variables (including firmware versions, cache size, controller, etc.) - a good testing program will show you how well the drive works over varying file sizes, a really good testing program will show you how well the SSD works at close to maximum capacity.

There are several testing tools, such as QuickBench (has not been updated for SL), BlackMagic Disk Speed Test, and others. Or just create your own tests with the files you most commonly use.

Rob

 

[nanofrog]

Slightly OT I guess, I've just installed 2 x 80GB X25-M G2's in RAID0 but have yet to decide on the block (or properly known as stripe) size. I'm thinking 64k but wondered if the cell size of the Intel drives needs to be considered regarding write amplification etc etc.

Given the way the data is stored on Intel's SSD's, 128K is best in this regard IIRC.

 

[playalistic]

Given the way the data is stored on Intel's SSD's, 128K is best in this regard IIRC.

Argh, I chose 64k in the end. Wondering whether I should blow the volume away and start again? Hmm.

 

[nanofrog]

Argh, I chose 64k in the end. Wondering whether I should blow the volume away and start again? Hmm.

That's up to you. There's no long term data as to how a smaller stripe would affect the drive's reliability that I've seen.

But the 128K size should offer an increase in throughput.

 

[playalistic]

That's up to you. There's no long term data as to how a smaller stripe would affect the drive's reliability that I've seen.

But the 128K size should offer an increase in throughput.

Cool. Well I think I'll leave it for a bit then in that case. There certainly is no shortage of speed /throughput right now

One more noob question. Am I right in thinking I can slap in another 80GB at some point and rebuild the array to include it, with no loss of data and without having to reinstall? Or am I on crack?

 

[nanofrog]

Cool. Well I think I'll leave it for a bit then in that case. There certainly is no shortage of speed /throughput right now

One more noob question. Am I right in thinking I can slap in another 80GB at some point and rebuild the array to include it, with no loss of data and without having to reinstall? Or am I on crack?

You can get it into a stripe set with the existing drive, but I'm assuming you're using software RAID (logic board + OS X).

So you won't be able to do what's called Online Expansion (can add drives to increase capacity while retaining data). Instead, you'll have to make a backup of any files you need first, then make a set of the two drives. The initialization step will wipe any existing data, and why you must backup first (even with a proper hardware controller, it's still a good idea anyway, just in case). Install the OS, and restore any files from backup.

 

[playalistic]

You can get it into a stripe set with the existing drive, but I'm assuming you're using software RAID (logic board + OS X).

So you won't be able to do what's called Online Expansion (can add drives to increase capacity while retaining data). Instead, you'll have to make a backup of any files you need first, then make a set of the two drives. The initialization step will wipe any existing data, and why you must backup first (even with a proper hardware controller, it's still a good idea anyway, just in case). Install the OS, and restore any files from backup.

OK thought as much. Cheers. I have a time capsule to save my ass if anything fails so no problems there

 

[VirtualRain]

That's up to you. There's no long term data as to how a smaller stripe would affect the drive's reliability that I've seen.

But the 128K size should offer an increase in throughput.

The 64K stripe should work just fine for reading.

Where a large stripe size benefits SSD's is on writing, particularly when the drive becomes used up and you start getting hit by the write-erase block penalty.

As everyone knows by now, a whole block needs to be read and rewritten if any portion of it is used. I recall anecdotal information that Intel uses a 128K block size, implying that a stripe of 128K would be ideal, but some tech sites seemed to suggest that most SSD blocks are 512K in which case, the largest stripe option available would be the best.

At any rate, you may as well run your array with 64K stripe size for a few months or more until you feel the need to rebuild the array, at which time you can do a secure-erase and restart with a 128K stripe size.

 

[nanofrog]

The 64K stripe should work just fine for reading.

Where a large stripe size benefits SSD's is on writing, particularly when the drive becomes used up and you start getting hit by the write-erase block penalty.

As everyone knows by now, a whole block needs to be read and rewritten if any portion of it is used. I recall anecdotal information that Intel uses a 128K block size, implying that a stripe of 128K would be ideal, but some tech sites seemed to suggest that most SSD blocks are 512K in which case, the largest stripe option available would be the best.

At any rate, you may as well run your array with 64K stripe size for a few months or more until you feel the need to rebuild the array, at which time you can do a secure-erase and restart with a 128K stripe size.

I was thinking of writes, as that's when wear/damage occurs to the drive. Hence the 128K suggestion.

Hopefully, playalistic would test the write throughputs as well, but I should have clarified.