SSDs and RAID 0 - advice on HDDs please

[Plekto]

All you need to do with Mac is copy the drive to another partition and it will boot.  Carbon Copy CLoner or Super Duper do this easily and you can schedule it, no need for an actual RAID 1 set-up.  Obviously Windows is more complicated.

Such tools also exist for Windows, but the point of RAID 1 is in case of a critical hardware failure(whole drive bricks).  $60-$80 for a second drive as a mirror is far cheaper than even a tape drive.  The motherboards all have this capability as well now, so why NOT use it?  RAID 0 for boot, though, is asking for trouble.

Again, not with Macs --- you can use the OS software to raid partitions.  Lloyd and I tested RAM disks and they fell WAY short in the performance compared to even a simple 2-drive stripe (RAID-0) on a pair of off-the-shelf SATA 2 spinners, at least on Mac.

This is a myth, though, since it's the same INTEL boards running most Apple machines.  Partitioning the drive doesn't deal with the bandwidth and i/o issues of having multiple partitions on the same drive or multiple drives on the same channel/chain.  Now, Apple does better here than Windows.  Windows is officially I/O brain-dead by comparison.

Note - by Ram disk, I generally meant a physical DDR based hard drive.   Or a simple small SSD.  For a swap or temp space you don't need a very large one, either.   The typical solution then is to just drop a 4-16GB SSD in the machine and use it for that.  Sometimes, though, using physical (system)RAM can help for little or no cost - better and cheaper than a new drive and running RAID.  Versus nothing at all, even a 1GB ram disk like this is a god-send.  Shoot, just moving the swap file to a second drive other than the OS drive is a good 50% speed boost.

I've experimented as well and nearly RAID 0 speeds are possible in Windows if you just drop the swap and temp directories to a SSD.(bit trickier with Apple here, which is why you didn't notice much difference - since Apple has it set up to not be easy to alter its default swap/directory assignments)  Also the typical end of program disk-thrashing is GONE so you quit and your machine is instantly ready.(big issue with Windows, IMO)  SSDs are amazing, really.

Not necessarily. I am running my OS on a pair of WD 640 Caviar Black drives in RAID-0, not the RE versions -- again using the OS RAID capability, no controller card and I get very fast boot, I/O and a huge, fast desktop for dropping stuff on.  My image storage array is on a 4-drive RAID-0 of WD Caviar Blue drives -- two partitions with the fastest outer partition of each drive in it's own dedicated 4-drive R-0 array for scratch...

A 4 drive RAID 0 array X2 on the same 4 drives is a time bomb waiting to go off.   Anything glitches and you're gone.  Now, I can see RAID 0 for a large file repository/applications drive, but the OS should be as bulletproof as possible, IMO.  Restoring files isn't a big deal.  Restoring and installing a new OS is a nightmare for Windows(less so for Apple, you're right)

[Jack Flesher]

A 4 drive RAID 0 array X2 on the same 4 drives is a time bomb waiting to go off. Anything glitches and you're gone. Now, I can see RAID 0 for a large file repository/applications drive, but the OS should be as bulletproof as possible, IMO. Restoring files isn't a big deal. Restoring and installing a new OS is a nightmare for Windows(less so for Apple, you're right)

Per my earlier reply, I have regularly scheduled back-up copies of my OS stored on my machine, one done weekly and one done daily, both of these are fully bootable, so no time at all spent "rebuilding" -- just a re-launch.   Also, why I feel comfortable running a R-0 for my main OS boot -- yes it has 2x the chance to fail and why it is backed up with bootable copies right there -- meaning two or three minutes tops to be back up and running should that RAID fail.  I have been running it that way for over a year now, so maybe I am due, but then I usually replace drives about every 18 months with new ones anyway...

Next OS boot disk will for sure be an SSD, and a 128 is probably big enough for my needs if I use the big array for image I/O -- little slower to process raws out since I'd be reading and writing to the same physical array, but even then a 4xStripe is pretty darn fast.  Hoping to see what CS5 offers before I have to do the SSD OS -- hoping we won't need a fancy dedicated scratch because if we do, I'll probably go to a pair of smaller SSD's and stripe them and do not look forward to that expense just for scratch.  If CS utilizes RAM for scratch (as it should have back with CS3) and only needs scratch for really massive files, then I could just point to the image array and let it use available space there for the odd occasion I might need it.

[Farmer]

All you need to do with Mac is copy the drive to another partition and it will boot.  Carbon Copy CLoner or Super Duper do this easily and you can schedule it, no need for an actual RAID 1 set-up.  Obviously Windows is more complicated.

Not really.  Windows 7 backup will place a VHD (virtual hard disk) image on another drive and it can then boot to that if you like.  To do it exactly as you suggest above can be done with Windows based apps in exactly the same way.  So, you have a choice of OS native or 3rd party methods to achieve this.  No one needs a RAID 1, but it is convenient.

Again, not with Macs --- you can use the OS software to raid partitions.  Lloyd and I tested RAM disks and they fell WAY short in the performance compared to even a simple 2-drive stripe (RAID-0) on a pair of off-the-shelf SATA 2 spinners, at least on Mac.

It's no different with Windows, where the OS makes use of RAID support on a mainboard.  Note that this can be significantly slower than hardware based RAID, particularly if you're making high use of the CPU for other things (such as image processing).  Both native and hardware RAID are available.

Not necessarily. I am running my OS on a pair of WD 640 Caviar Black drives in RAID-0, not the RE versions -- again using the OS RAID capability, no controller card and I get very fast boot, I/O and a huge, fast desktop for dropping stuff on.  My image storage array is on a 4-drive RAID-0 of WD Caviar Blue drives -- two partitions with the fastest outer partition of each drive in it's own dedicated 4-drive R-0 array for scratch, the larger inner portions in a separate R-0 for large, fast image storage and access, again OS RAID, not RE drives, basic off the shelf drives and with 4 of them, very fast.  Of course since that's working images in R-0 which is NOT redundant, it is backed up locally.

I've often wondered about the utility of using the same physical array for two logical arrays in this manner.  Short striping for performance (ie the outer sectors) theoretically improves peformance, though mostly for benchmarking tests compared to real world use), but if you are also attempting or potentially attempting to access information from the other logical array at the same time as scratch is being accessed then you necessarily have degraded performance.  I guess the question is how often would such a conflict occur.  The answer depends on available system RAM and what you're currently doing, of course.

[Plekto]

It's no different with Windows, where the OS makes use of RAID support on a mainboard.  Note that this can be significantly slower than hardware based RAID, particularly if you're making high use of the CPU for other things (such as image processing).  Both native and hardware RAID are available.

SSDs are really hindered by the interface, and doubly so by on-board controllers.  Hopefully faster options become more mainstream.

http://www.techwarelabs.com/reviews/storag...oint_raid_3520/
Even moving to PCIe from SATA 2 for a raid card is a massive jump.  Again, these will become "normal"(and reasonable to own) in a few years.

[Jack Flesher]

I've often wondered about the utility of using the same physical array for two logical arrays in this manner.  Short striping for performance (ie the outer sectors) theoretically improves peformance, though mostly for benchmarking tests compared to real world use), but if you are also attempting or potentially attempting to access information from the other logical array at the same time as scratch is being accessed then you necessarily have degraded performance.  I guess the question is how often would such a conflict occur.  The answer depends on available system RAM and what you're currently doing, of course.

The only reason I partitioned off the outer rim for scratch is to keep the absolute fastest portion of the striped array easily accessible for scratch.  Drives fill from the outside in, so as I load images on the main array, I am pushing the free space further and further inward.  Thus scratch could theoretically get slower and slower.  As for real world, I made my own CS benchmark to test it, using real images, multiple layers, sizing and sharpening routines in CS, and the results were resoundingly superior performance, shaving the single drive at 2:25 down to just over a minute on the 2-drive scratch, then the 4-drive array shaved another 20 seconds or so off the 2-drive stripe.  I am not usually needing to write to the image storage array whilst I am processing large files in CS -- they get saved to the array after the CS heavy lifting, so there is not usually any I/O conflict between those partitions.  But clearly if one was regularly accessing the larger partition at the same time as scratch, the I/O conflict would slow things down.  

If you're saying you don't believe the outer rim is that much faster, take a free drive and partition off 50 gig outer partition, then a large middle partition and then another 50G partition at the end.  Now write say 5G of data from your desktop to the outer 50G, then write the same 5G to the inner 50G and you'll see a significant time difference. Now pull them off back to your desktop and time in reverse, you'll note similar performance gains from the outer partition.

[Farmer]

If you're saying you don't believe the outer rim is that much faster, take a free drive and partition off 50 gig outer partition, then a large middle partition and then another 50G partition at the end.  Now write say 5G of data from your desktop to the outer 50G, then write the same 5G to the inner 50G and you'll see a significant time difference. Now pull them off back to your desktop and time in reverse, you'll note similar performance gains from the outer partition.

No, I know the outer rim is faster - short striping clearly does have some benefit, but whether that benefit is worth the loss of use of the rest of the drive (potentially) in a real world situation (ie is the time saved actually reducing the time it takes to do the job) is the question.

[Jack Flesher]

No, I know the outer rim is faster - short striping clearly does have some benefit, but whether that benefit is worth the loss of use of the rest of the drive (potentially) in a real world situation (ie is the time saved actually reducing the time it takes to do the job) is the question.

Okay, got it. In my case the answer is the time saved by the scratch stripe is not affecting the time it takes to do the job at any point in the chain. To the converse the scratch is speeding up my large file CS processes significantly, so for me it is a definitive win

[John.Murray]

If you're saying you don't believe the outer rim is that much faster, take a free drive and partition off 50 gig outer partition, then a large middle partition and then another 50G partition at the end.  Now write say 5G of data from your desktop to the outer 50G, then write the same 5G to the inner 50G and you'll see a significant time difference. Now pull them off back to your desktop and time in reverse, you'll note similar performance gains from the outer partition.

It's called Short Stroking and has been a common practice by Database Admins for years.  Here's a nice article along with some benchmarks....

http://www.tomshardware.com/reviews/short-...hdd,2157-2.html

BTW - Don't be tempted to use the rest of the drive as a 2nd partition for anything else production wise....  this will kill any benefits of short stroking.

[Brammers]

Noticed this thread is still going.  I went with 2x 500GB F3s as an OS + Apps drive in the end, and demoted my old OS drive to scratch disk duty.  Everything is a lot faster than before and it's now plenty fast enough for me to manipulate my standard sized panos - up to 12 24mp images.

My larger ones still chug a little, so I've got the option of replacing the old OS disk with an SSD in the future.  

Just to clarify a couple of points from the 1st page, when I was talking about RAID Vs SSD in terms of speed I did of course mean RAID magnetic HDDs Vs a single SSD - both of those combos coming in at about 100GBP.  Also, I'm perfectly fine with RAID 0 as an OS drive - reinstalling an OS really isn't a problem for me, I think my backup routine is pretty good nowdays and it honestly doesn't take more than an hour or two to be exactly where I was before.

Thanks all - and good luck to those of you struggling with 4x HDD RAIDS Vs 2x SSD RAIDS!

[Christopher]

Thanks all - and good luck to those of you struggling with 4x HDD RAIDS Vs 2x SSD RAIDS!

Well as long as there is no TRIM command for RAID arrays using a MLC based SSD RAID 0 System would just be a waste of money.