View Full Version : RAID for newbies

Dan Clark
09-01-2002, 03:57 AM
Gregory, Rick, thanks for the suggestion and encouragement. Where to start, when you don't know anything???

I'd like to learn what results I can realistically expect to get by adding a RAID setup to our existing 350 and 400 B&W G3s. We spend virtually all of our time in Photoshop, though most of the time our files are not huge. We shoot with digital cameras that generate 18Mb RGB files, so most layered files are in the 20-60Mb range. We sometimes are dealing with layered files that get up to 200-300Mb, though that doesn't happen very often. Systems have the 1 Gig max of RAM, with 400-800 thrown to PS. We're running OS 9.1. Typical scratch disk range is 1-1.5 Gigs, just partitioned on the 6-9 Gig internal HDs.

Gregory, when you say 53MB/s, does that mean a layered file that size (once opened in PS) would open or save in one second? A hundred Mb file in two seconds? Do you have the PS files and scratch disk on the same RAID setup? How 'bout the OS and apps?

I've seen some B&W G3s with an Adaptec 29160 card, running 2 9Gig Seagate drives, I think. Is this a good setup? Is there a significant real-world difference in going to the G4s?

OK, that's all the dumb questions I can think of for now. Thanks in advance for the enlightment.


09-01-2002, 07:29 AM

Today's drives far outperform even drives of 18 months ago, and the smallest are 18GB. Even a single 36GB 10K Cheetah can deliver a sustained benchmark write of 50MB per second. I'd start with one and add as needed.

Maxtor Quantum Atlas 10K III has extremely good sustained reads, and is another good option, again, I'd stick with 36GB unit.

Adaptec doesn't have OS X support even yet - which is why I'd avoid them unless you've already committed to some. On PCs Adaptec is fine, on the Mac, you might want the ATTO cards.

But I would look at ATA HARD RAID first. You can have a large RAID setup for $350. Half the costs of SCSI. You could always use it for backups along with SCSI of course.

Spread the work load, so that scratch is on its own drive, otherwise, you get head thrashing. Usually scratch is on the outer (first) partition of a RAID. Most IDE drives squeeze a lot more tracks per platter. With SCSI while the density is also going up, you're talking about 9-18GB per platter, so it is easier to find and write files. Easier to allocate work load across drives.

Normally you could create a 4 drive RAID and see 200MB/s but on the B&W that is not possible, not on the PCI bus using the 33 MHz slots anyway. There's a bug. I could only if I put the Adaptec 39160 in the video slot 39160 is 'dual-function' and benefits from 66 MHz PCI slots). It's that 200MB/s sustained writes that is, in part, the reason why people choose SCSI. Reliability, ability to scale, support for 15 drives per channel, better I/O and lower cpu overhead (less so today). But at a cost.

Ultra320 addresses the fact that three 15K Cheetahs can saturate a single channel to 210MB/s, which is also the max that today's PCI bus can handle. You need an XServe to get past that bottleneck to the next level of 520 (?) MB/s or hopefully Apple's "next big thing" - whatever and whenever that happens. (some of us dream of waking up Christmas morning to find a Power4 cpu from IBM in our Macs!)

RAID tries to make up for the fact that disk drives are the slowest component.

The G3 delivers memory at 90MB/s (99MB max) but put a G4/500, and it climbs to 165MB/s. Get a real G4 and it hits 333MB/s. Now, do you want your disk drives to deliver 50MB/s? or 80MB/s? No. You can buy IDE or SCSI now, and take it with you when you do move to a G4 and reap more benefit. You can always use IDE and/or FireWire for backup, slower storage.

IDE has come a long way. Serial-ATA hopes to bring 150MB/s, 800 Mbps FireWire 4-channel RAID, HARD RAID, and then there is OS X. If you want to do RAID, you need software, or built-in harddware RAID so you don't need RAIDtoolkit or SoftRAID ($100-150). OS X is worth the cost just for the built-in RAID. Hopefully some of this is going to arrive in 2003, along with the faster PCI bus, 66 MHz slots, etc. but you could be waiting forever. I'd budget for 2003 major over-haul.

StorageReview.com and XLR8YOURMAC.com have a lot of information on upgrades and storage. Especially look at Intel's latest benchmarking suite of tools, surprising numbers on today's IDE drives.

Again, I'd consider looking for a G4 for your work. Faster bus, AGP, pushes more data thru memory, better support for SCSI's Ultra320 or ATA/66 and ATA/100, and magnitude above G3's. Even if it means selling one B&W (likely to fetch $650) once the G4 is firmly tested and in place.

Once your software needs are met by OS X versions, and you've got that budget item taken care of, I'd move to 10.3 in 2003 if not before. Great built-in RAID support, fast, and preinstalled on your G4's.


[This message has been edited by Gregory (edited 01 September 2002).]

09-01-2002, 04:30 PM

?I think striped arrays (RAID0) is one of the best ways to speed up Photoshop. Photoshop does not do that great of a job keeping even your standard 50MB picture file within ram and that's where a fast array will speed you up.

?As you work a picture PS is storing gobs of data-History, layers, prefs and the more you want to be able to go back with multiple undo's the more disk space you need.

?I have a habit of doing most of my photo work at insanely high resolution. I just love a 1400dpi print job. So when working a 8x10 picture I am pushing over 300MB file size. In no time at all I canrun out of a 5 gig scratch disk. Your average 50MB picture will use a tenth of that, so you should be OK with your 1 or 2 gig scratch. When you upgrade to Photoshop7 you'll find you need even more scratch space though since PS7 saves a bunch more temp and history files than 6 did.

?A fast scratch array is the cheapest way to speed up Photoshop. The more data that is swapped back to disk the more that your RAID will speed it up.

?As Gregory said, scsi arrays are expensive. And because of the WRITE limitation of the B&W (also the first G4, the Yikes, which had the same memory controller as the B&W) I don't think you gain enough for the dollars to install a scsi RAID.

?On the other hand ATA133 Hardware RAID cards and two quality drives like BarracudaIV's are a great investment. The RAID database we have shows quite a few performance numbers for the B&W with both scsi and ATA133 hardware RAID cards, might be worth your time to glance over it. RAID Database Here (http://www.macgurus.com/ubb/Forum1/HTML/000289.html)

?The other thing might be just as valuable would be installing faster G4 zifs in your B&W's. Gregory and I both have 500 G4 cpu's in our B&Ws, much better than the old 350 or 400 G3 zif, especially for Photoshop which is so dependent on Altivec, the core logic that makes G4's faster. It looks like we might soon be seeing up to 800 or even 1 gig zifs for our B&W's. That should really help.

?You will need to check out your ram for quality before you do a G4 upgrade though, G4 cpu's are MUCH less tolerant of slower ram. If you go that way we can set you up with the test utilities and a little guidance on what constitutes spec for the B&W.

?RAID is becoming more common today, especially with Apple including it in a software form with OSX, I think we'll see more and more attention paid to RAID in the future. Unfortunately with the B&W we can already push the limit of the PCI bus with single drives. The new towers from Apple moved the bar up significantly and I REALLY look forward to testing the limits with the higher top end limits.


09-19-2002, 12:21 AM
Ricks, Gregory and Dan,

While I know for a fact that I'm no Photoshop Guru and as much as I would love being able to afford a brand new, Dual-1.xx GHz Power Mac with a Fibre Channel RAID, I've always just used a RAM Disk for my Photoshop Scratch.

As I am only running a G3/500 upgraded 9500 with a measley 288MB or RAM, I found that was a lot faster than using (a quite outdated) a 10K Cheetah (running off of a Adaptec 2930, like I said I am poor). Considering that Christmas is rolling around and I'm gonna up my RAM, install a (PCI- Charisma) Radeon (just ordered it yesterday) and finaly try a shake at X (via X-Post facto) , what should I be looking for Scratch Disk Speed?

ie- I know that OS-X is supposed to manage memory better than Classic, but is X even capable of creating a RAM Disk?
Should I be looking into a ATA -H/Ware RAID in the future???
It's not like I have to have any sort of accuracy that you guys might need, but just like any self-respecting musician, I procrastinate to the last minute to make Show fliers.

Sorry I jumped in on this thread so late, but it's been stormy here lately and I didn't dare risk another modem.


"I made a conscience decision in a semi-conscious state"

09-19-2002, 01:19 AM
Hey Bill,

?Welcome back to the land of the connected. New modems at least got cheaper, still I feel for you having to waste bucks replacing zapped devices instead of buying upgrades. (We LOVE UPGRADES)

?First, no ATA HArdware RAID for you. Sorry, but they don't work any faster than a single drive in pre G3 Macs, not enough PCI bandwidth I'm afraid. In fact testing showed that a single drive out performed two drives on the Acard.

?The Miles2 and a fast Cheetah or two is still the king. I am using a few of the cheaper Atlas III 10k drives instead of Cheetahs, they do a good job also. I don't know what you can get out of that 2930 or even if it would be supported in OSX on your 9500, Gregory will have the low down on that though. If it's possible to build a RAID using that card you might save a few bucks that can go towards more RAM. (OSX loves ram, ram is good)

?I don't think I have ever heard of a way to make an OSX ram disk. And yes, OSX uses ram really well with an active memory manager and all, but I think you'll find that Photoshop will need a large scratch disk just to keep from running out of places to store stuff you're working on, you'll overrun even a gig of ram in no time. (I was having trouble staying within a 5 gig scratch disk, yowser)


09-19-2002, 06:20 AM
Put one of those UPS units between the phone line and your modem!! Maybe a phone/fax surge protector as well - you can use two - I do, I need to shield my DSL modem. There are surge protectors for RJ-11 and/or -45 and no computer should be without one.

The guy that did RAMbunctious did an OS X version as well. *nix does have virtual volumes, aka memory used as a RAM disk, but it isn't or wasn't implemented or easy to add. Haven't read much or heard of people using it. You can create RAM disks of 256MB+ under OS 9.1 if you go that route.

ACard has a nice $169 Ultra160 LVD card if you do decide to go for some newer Cheetah or Atlas drives.

09-19-2002, 10:20 PM
Gregory: <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Put one of those UPS units between the phone line and your modem!!<HR></BLOCKQUOTE>

I know, I know...

but you have to admit Ricks' <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>New modems at least got cheaper, still I feel for you having to waste bucks replacing zapped devices instead of buying upgrades. (We LOVE UPGRADES)<HR></BLOCKQUOTE> is soooo true.

Since the modem bit the dust though, I just unplug the phone line since it's within reaching distance when you hear the Thunder roar. When the last one ate it, we were out of town and of course, I didn't use the blatantly obvious prevention method mention by Gregory. My learned mistake.
Oh well, I bought a used PC one for $15.00 and it's been doing OK even though it gets really HOT.

As for Scratch Disk suggestions, I just opened the Drive and RAID Database Page, and of course I didn't notice any comparisons between Miles2 and the ACard (AEC-67160M Ultra160 SCSI Adapter which is what Gregory mentioned) nor of the ACard vs. the ATTO.
Of course, the ATTO is too much money for me at this point anyways.

Thanks for the input....Now I'm off to post yet another silly question in this Forum!!! http://macgurus.com/infopop/emoticons/icon_biggrin.gif


"I made a conscience decision in a semi-conscious state"