RAID 0 and scratch discs

[leo s.]

Seeing as you need to have your scratch disc and OS on separate physical drives

to get maximum benefit in a NON-RAID scenario, would it then follow that to do

the same with a RAID 0 setup, you need 2 separate arrays (ie 2x2 drives) to

achieve best available performance?

 

If this is the case, do all RAID controllers let you setup separate arrays? Can

anyone recommend a controller that will allow this? I'm not sure if my bios

will, although it does have RAID.

[mtwhite]

You are correct in that you would need a separate raid array if you wanted a speed boost regarding scratch files, but I would strongly advise against <a href="http://en.wikipedia.org/wiki/RAID_0#RAID_0">RAID0</a> on your main OS drive. The 0 stands for the amount of data you can expect to recover from any of the drives if a single one of them fails. It's a disaster waiting to happen. <A href="http://en.wikipedia.org/wiki/RAID_1#RAID_1">RAID1</a> is good, <A href="http://en.wikipedia.org/wiki/RAID_5#RAID_5">RAID5</a> is better.

[colinsouthern]

Much of the "benefit" of seperating scratch disks from OS disks - from data disks - from app disks (all 15,000 RPM SCSI in striped, mirrored arrays of course) is FAR more theoretical than it is practical.

 

Usually a better solution is to ensure your PC has sufficient RAM so that it doesn't need (or in fact even use) the scratch disks. RAM is cheap - and a LOT faster than any spinning HDD will ever be.

[leo s.]

Thanks Matthew,

 

I think I'll take the risk with RAID 0, but I'll make regular backup images of my main OS drive using Ghost, which should let me recover a drive if one goes!

[leo s.]

Colin - thanks for your reply.

 

I've ordered enough RAM (8GB) to max out my mobo, and the fastest I could get (of good quality anyway). But, for those time I do run out (at least until CS4 and hopefully more RAM support), I want a fast scratch disk... or at least faster than the normal sluggishness! Any idea just how much of an increase in performance I can get from RAID etc?

[leo s.]

I suppose I'd better say what my new system is:

 

Asus Striker II Formula mobo

 

Intel Core 2 Quad Q9450

 

Tuniq Tower 120 CPU Cooler

 

8GB (2x2GB) Corsair TwinX DDR2 PC2-8500 (1066MHz CAS 5-5-5-15)

 

BFG GeForce 9800 GTX 512MB GDDR3

 

Tagan TG800-U33 800W 2-Force II Series PSU

 

Icy Box IB-138SK-B 3.5" SATA HDD Caddy

 

Microsoft Windows Vista Home Premium 64-bit

 

HDDs:

 

Seagate 250GB Hard Drive SATAII 7200RPM 16MB Cache - OEM x2

 

Seagate ST3250310AS 250GB Hard Drive SATAII 7200rpm 8MB Cache - OEM

 

For backup purposes via the caddy:

 

Maxtor 500GB Hard Drive SATAII 7200rpm *32MB Cache* - OEM

 

 

I'll be doing a bit of gaming too, hence the slightly above average GTX ;)

[cudacar2000]

Theoretically, a RAID 0 array will be twice as fast as a single disk for totally random, small reads/writes. In a totally sequential environment, on a totally defragged disk, it would be much closer to the same speed (no benefit to RAID 0).

What you will see will be somewhere in between those extremes. Buying a RAID controller with a good amount of cache on it will help even more.

[bgelfand]

My older version of Ghost does NOT support RAID volumes. Are you sure your version does?

[colinsouthern]

"8GB (2x2GB) Corsair TwinX DDR2 PC2-8500 (1066MHz CAS 5-5-5-15)"

 

You might want to double-check your order - usually a "2GB Twin Kit" from Corsair is 2x 1GB - so you're going to have 4GB all up, not 8GB. Last time I checked, Corsair didn't make a 2GB unbuffered DDR2 stick.

 

"I'll be doing a bit of gaming too, hence the slightly above average GTX ;)"

 

Damn - and there's me stuck with my dual over-clocked 8800GTX installation on my quad-core extreme edition CPU running at 3GHz (with twin WD Raptor 10,000 RPM drives in RAID 0 for OS and dual 400GB HDDs in RAID 1 for data ...

[steven_clark]

If you really want high performance you might just want to look at a Raptor for the drive your scratch disk is on.

[leo s.]

stan - Thanks for your reply,and the info. I seem to be getting conflicting info though - I have read that with RAID 0, there is no performance gain with having hardware w/cashe.

 

Brooks - Thanks for the heads up. I'm not sure if the version I have supports RAID. I'll look into it, and if it doesn't perhaps a newer version does. I came across an FAQ on RAID that had a section on restoring a broken RAID array last night, so it does look like it's possible to do with something or other, but I haven't had time to read it yet.

 

Colin - See: http://www.corsair.com/_datasheets/TWIN2X4096-8500C5DF.pdf

 

Sounds like very nice system you have there. How come you're only running @ 3GHz? You should be able to get @ least 3.6GHz, if not 4.0GHz! I wanted a QX chip, but they are just a bit too expensive for me! I may get a second card for SLI later on in the year if/when prices come down a bit ;)

 

Steven - I was looking at those, but a friend told me they were a bit noisy compared to 7200rpm drives. I may have to reconsider... Thanks for your input.

[colinsouthern]

"Sounds like very nice system you have there. How come you're only running @ 3GHz? You should be able to get @ least 3.6GHz, if not 4.0GHz!"

 

It's just running the standard cooling, and I don't need anything faster anyway. I've heard of this chip being overclocked to over 5GH with an extreme cooling technologies unit (-60 to -40 deg C). Also, not much point in ramping up the CPU if the memory doesn't keep up - at present I'm running 8500 RAM (4GB total) - tried to get the 10,000 RAM, but they national suppliers couldn't supply it - so I just gave up and ran with what I had. Next MoBo will probably be with a dual extreme-edition quad-core (Intel Skulltrail) and a couple of 9800 GTXes.

[garrison_k.]

"Steven - I was looking at those, but a friend told me they were a bit noisy compared to 7200rpm drives. I may have to reconsider... Thanks for your input."

 

I second Steven's recommendation. I run raptors and you wont hear them over the fan's. I raided two as well. WD now sells ones with a plastic transparent cover for the gamers. The warranty is less as the cooling isn't as good as their normal non "X" brand. For small insurance factor, I put in Scythe fluid ball bearing fans for the extra cfm and noise reduction.

 

Your original question re 2x2 drives for C is a great way to go. Another 2x2 raided drives for D drive to hold your scratch, bridge cache, lightroom libraries etc. I also moved my "documents and settings" to D drive for easy back back up to externals. Just drag it all over in one move. It sounds like you have a budget so I'd consider getting four rapator drives for the above purpose and use your current ones for storage. Raptors will last you for years.

 

I use ghost 2003 and have no problem with backing up (over the raid) the entire c drive or just the image. When you get to the first screen in Ghost, I have to enter "A" for abort and this somehow brings me to the normal menu screen to make the image. If you have trouble, try this route. I have two boxes with raided drives and do ghost back-up's regularly. But I've had trouble with Acronis with raid's. It seems to make the image alright, but wont re-store it and corrupt warnings soon arrive. Some people with raid set ups that are restoring from ghost often need the raid controller drivers (on floppy) close by before you can proceed. Maintaining raid array's is not for the faint of heart :)

 

Good to see you're not cheeping out on the power supply too. Nice box, good luck with it!

[cudacar2000]

RAID 0 improves performance by alternating blocks on 2 different drives. Effectively this means you have 2 drives accepting writes - so if a drive has an average latency of 10 ms (for example) then you would be able to write (or read) 2 blocks every 10 ms. So for random busy environments you would see a great improvement - but sequential reads/writes happen with much smaller latencies, which is why the benefit is less.

Cache does 2 things. When you do a write, it goes into cache (memory on the disk controller) which is much faster than the disk. If you do small writes, the cache will hold many writes, but if you do large writes, then the cache (obviously) holds fewer writes (although teh same number of blocks. The cache (on a well designed controller) also lets you read ahead - effectively guessing that if you read block number 2412, you will probably read block 2413, and it reads it before you ask. Also, if done right, the cache will allow you to read from the write cache, so if you write a block, then read it back a little later (as long as it was not overwritten) it will skip the disk snd come out of cache directly.

There are too amny variables to know how effective it will be, but you will get some benefit from RAID, and some from the cache. I would not say that RAID 0 reduces the need for cache at all though.

[leo s.]

Colin - You'd probably be fine @ ~3.6 on air/stock cooling, and a little extra speed couldn't hurt. You should give it a go and see how your temps are IMHO.

 

Garrison - thanks for your input. I was actually thinking of (1x2)+(1x2) arrays, but I'm still undecided. (2x2)+(2x2)would be a bit much for me, and I wouldn't have enough SATA ports for that anyway. I only have 6, and 2 are used up by DVD + HDD caddy.

 

I'm considering getting a raptor for a scratch disc though, and my C:/ will be a RAID 0 array of 2x 7600rpm, 16mb cashe drives. I've literally just finished putting the system together, and will see if it boots tomorrow as it's getting a bit late now.

 

Glad to hear that at least one version of Ghost works with RAID. I should know within the next couple of days if mine does!

 

Two systems ago my PSU (cheap rubbish that came with the case)blew up, and scared the crap out of me, so I know better than to skimp on PSUs now ;) The last system I built has a Tagan too, and it's a very under rated brand IMO - it's well built, and hasn't let me down yet!

 

stan - thanks for that info. I think I'll start off with software RAID and perhaps pick up a card later if I see a nice one for a good price. It'll be interesting to compare the performance.

[colinsouthern]

"So for random busy environments you would see a great improvement - but sequential reads/writes happen with much smaller latencies, which is why the benefit is less."

 

Keep in mind also though that with Raid 0 you're also doing simultanious reads / writes that effectively doubles the bandwidth (or halves the drive transfer bottleneck), which ever way you want to look at it.

[leo s.]

Just for future reference, I got my box up and running, but I had problems using Ghost with the RAID 0 array, just as Brooks warned. It may just have been a problem with my DVD/CD burner(I'm not sure at this stage), but it turns out there are issues with Ghost and RAID/SATA arrays. Hardware RAID is less lightly to be incompatible than software RAID apparently.

 

In the end I came across another solution by using DiskWizard (http://tinyurl.com/27y63t)which is free, but will only work if you have Seagate or Maxtor drives installed. However, if you don't have Seagate or Maxtor drives installed, Acronis True Image Home 11, which is basically the same software as DiskWizard (minus a few small features) will be able to do the same job.

[garrison_k.]

Yes there are issues and many have trouble working around it. But it is possible, Ghost and raids of all sorts have been used for years and I have two software raid o sata boxes that I use Ghost on.

 

Can you be more specific on what sort of trouble you had, Leo? I'll do my best to help you out but I'm no expert and it's a little tricky sometimes getting over the raid drivers. I had one "tech" fellow say it couldn't be done, a day later another tech guy did and knew all the reasons why people have trouble and walked me though it. I'm using Ghost 2003 on cd. Is your boot set up to go to your optical drive first?

 

Be careful with Acronis. I went through these exact same steps. Had trouble with Ghost, went to Acronis, Acronis did the image alright, but wouldn't restore the image. Over and over, I made images and they all ended up being corrupt and not accepted when I tried to re-store. Ghost is the preferred method as in the case that if one drive in your array may die, you can just replace the guilty party and re-store with your ghost image and not lose anything other than time. You wont be able to do this with Acronis as they implement more security to stop people cloning machines. Which, for your safety with a raid set-up, you want to be able to do this with Ghost. Ghost 2003 was one of the last Ghost app's that would let people clone. The software manufactures freaked and pressured them to change it. And they did with later versions. With Acronis, and today's other image makers, if a drive fails and you try to restore your image on a replaced hard drive, the software will recognize this effort and will stop and go "Hey, this isn't the same hard drive this image came off of, sorry, you're out of luck."

 

Not sure which Ghost you are using and if it's on cd or not, but try this;

 

-restart, hit F8 on second screen of reboot. if nothing happens, let it boot and then restart again. this time on the second screen of reboot, try F12. One of my boxes needs F8, the other F12.

 

-you'll know you're in luck when you can make a boot choice and choose your dvd drive which will have your ghost disc

 

-then the weird part, select A for abort.

 

This doesn't abort but gets you to the familiar ghost screen where you can make your images. Good luck, it is possible to Ghost and is the preferred method.

[leo s.]

Thanks for your reply Garrison,

 

I've been trying to use the version that comes with Hiren's BootCD 9.4 (version 11.0.2). I did set boot priority to boot from CD first. The problem seems to be that it won't load drivers properly (at least 1/2 of them) eg. atapicd.sys, and Ghost fails to load due to that. I'm going to try again if I can get hold of another version of Ghost, and with a floppy drive which I'll borrow from my current box.

 

I've also tried using a USB card reader and SD card (There's a page which I can't find right now on how to make it somewhere on Hiren's site), but I think it will only work properly with memory sticks rather than with a card reader.

 

I'm not sure if your method will work with my current version, but I'll give that a go too. Perhaps in the mean time I'll try to restore with one of the images I made with Acronis.

[garrison_k.]

Keep us posted, Leo. Hows the box run, btw? Fast, I bet!

 

Another useful thing I did was make a disk with nLite. Once you are dialed in, and before you go gaming and on the net, make a disk with nLite. It will take your oem copy of Windows, the service pack(s), your drivers, and all your settings and make a nice tidy boot disk for you with everything all wrapped into it. Very helpful!

 

Good luck.

[leo s.]

It's not too bad, but I have yet to put it though it's paces. It certainly boots noticeably faster than it did before, and it was pretty fast to start off with... on my first attempted install of Vista, unbeknown to me Vista decided to install the OS on a drive other than my RAID array despite me specifying the drive I wanted! It was a good few hours (and lots of tweaking/driver updates) later that I noticed. After allot of swearing I disconnected all other drives apart from the array and reinstalled.

 

I really want to get an image of my OS that I can trust before I start installing lots of other stuff and over clocking. I'm also still waiting for the 1066MHz ram to arrive. In the mean time I have 2x 2GB of 800MHz ram in there. Once I get everything sorted I'll upgrade to CS3 and see how that runs. I still need to get a decent audio card before I can play any games. There was a card bundled with the mobo, but I don't trust the quality!

 

Thanks for the nLite tip Garrison - I'll have to check that out!

 

Does anyone know, if I upgrade to CS3, can I keep CS2 running on my old machine without having to buy a separate license?

[kelly_flanigan1]

Just install the newer version in another directory; and save the older one. One can have many photoshop versions on one machine at a time. Here is 1/2 dozen versions of photoshop on one computer; usefull if one teaches or has to move forward older files abandoned by newer versions<BR><BR><img src="http://i4.photobucket.com/albums/y148/ektar/PNdesktop/desktopcrop14.gif?t=1208734143">

[leo s.]

Kelly - Yes, but I'm talking about having the upgrade on my new box, and keeping CS2 on my old box, so not on the same computer. While I'm at it, also wondering about the same thing for C1 Pro!?

[leo s.]

I successfully restored my C:\ from a backup image via the DiscWizard boot disk in a test, so it seems I can rest easy now. I don't see any reason to tinker with Ghost any more.

[garrison_k.]

I know that feeling! Congrats, Leo.