PDA

View Full Version : Photoshop



TZ
08-28-2005, 09:14 AM
INDEX OF PHOTOSHOP ACCELERATION FAQs
The 4 Basic Hardware Principles of Photoshop Acceleration

Drive Configurations for Photoshop

Part 1: Use A Fast Startup Drive
Part 2: Use A Second Drive For The Scratch Disk[/url]
Part 3: Use A Fast RAID0 For The Scratch Disk[/url]
Part 4: Use A Separate "Users" Drive[/url]
Part 5: Use The "Work Disk/Scratch Disk Method"[/url]
Part 6: Use A Striped RAID0 Startup Disk

Machine-specific Photoshop Acceleration Strategy:

Hard Drive Comparisons:
74GB WD740 WesternDigital Raptor vs 160GB 7200.7 Seagate Barracuda
74GB WD740 WesternDigital Raptor vs 300GB 7200.8 Seagate Barracuda

Comparison of Photoshop Versions:

Photoshop 7 versus Photoshop CS
Photoshop Optimization (http://www.macgurus.com/guides/photoshopguide.php)
Photoshop FAQ
Photoshop Benchmarks (Discussion)
Photoshop scratch RAID (http://www.macgurus.com/forums/showthread.php?t=19970)
Photoshop Troubleshooting (http://www.gballard.net/psd/troubleshootpurgepsd.html)
Photoshop Test Utility (benchmarking) (http://www.macgurus.com/forums/showthread.php?t=20218)

Now, with CS2, we've got a situation where a really fast dual G5, boat loads of RAM, and the fastest possible startup disk are the prime ingredients for getting the best performance. Add to that the 4th part of the equation for those working with mongo files: a big, fast, and separate "Work Disk/Scratch Disk". For you particularly, I would suggest the WD/SD approach. In addition, max the RAM to 8GB.

From Adobe:
When you run Photoshop CS2 on a computer with a 64-bit processor (such as a G5, Intel Xeon processor with EM64T, AMD Athlon 64, or Opteron processor), and running a 64-bit version of the operating system (Mac OS v10.3 or higher, Windows XP Professional x64 Edition), that has 4 GB or more of RAM, Photoshop will use 3 GB for it's image data. You can see the actual amount of RAM Photoshop can use in the Maxiumum Used By Photoshop number when you set the Maximum Used by Photoshop slider in the Memory & Image Cache preference to 100%. The RAM above the 100% used by Photoshop, which is from approximately 3 GB to 3.7 GB, can be used directly by Photoshop plug-ins (some plug-ins need large chunks of contiguous RAM), filters, actions, etc. If you have more than 4 GB (to 6 GB (Windows) or 8 GB (Mac OS)), the RAM above 4 GB is used by the operating system as a cache for the Photoshop scratch disk data. Data that previously was written directly to the hard disk by Photoshop, is now cached in this high RAM before being written to the hard disk by the operating system. If you are working with files large enough to take advantage of these extra 2 GB of RAM, the RAM cache can speed performance of Photoshop.

PS CS2's new scheme of caching scratch disk data in RAM works only under Tiger, not Panther. It's also why there appears to be less scratch disk activity with larger amounts of installed RAM. CS hit the 2GB limit pretty quick, but not so with CS2.

.....But one still needs a really fast startup disk and a really fast scratch disk- especially for you jacob, because of the really large scratch disk file generated by those mongo image files of yours. It really wants to be on a separate drive from the system and user data. If you save the image file to the dedicated (no other files but CS2's temp file) scratch disk ala the "Work Disk/Scratch Disk Method", and it's a striped RAID of two or more drives, your operations will be quicker all around.

CS2 with a Giga bump and OS X 10.3.9.

Apparently there is a software conflict with the Giga Meter Extension and Adobe Creative Suite 2 resulting in what I described above. He said that they have worked on the issue and have a patch available, the correct version (1.0.1).

Photoshop Performance (http://www.macgurus.com/guides/photoshoperfconfig.php)
Photoshop Performance Benchmark (http://www.macgurus.com/forums/showthread.php?p=83824)
Photoshop Acceleration Basics 2 (pdf) (http://homepage.mac.com/boots911/.Public/PhotoshopAccelerationBasics2.3.pdf)

TZ
11-25-2005, 02:17 PM
From Barefeats:

... we are finding Tiger and Photoshop CS2 make a potent combination, especially since Tiger addresses the full 8GB of memory and Photoshop CS2 can create a memory cache of up to 3.5GB. The latest caching scheme is so effective, our 500MB file rotate dropped from 20 to 10 seconds
http://www.barefeats.com/cscs2.html

Photoshop CS2, though it supports up to 3.5GB of memory cache, actually turns over cache management to Mac OS X. Using Activity Monitor, we observed the OS grabbing up to 7GB of memory to use as cache for Photoshop CS2, the only user application running on our G5/2.5GHz Power Mac with 8GB of memory.
http://www.barefeats.com/tiger.html

1. Though the RAID 0 scratch volume did OPEN and SAVE as much as 200% faster than a single scratch volume, the typical PHOTOSHOP CS ACTIONS only gained 59% in speed.
http://www.barefeats.com/scratch.html

Our PS FAQ is written toward PS 7 and CS. There tends to be a regular discussion on SR forum on PShop and disk drives.

Photoshop Configuration (http://www.macgurus.com/guides/photoshoperfconfig.php)

G5 2.7DP, CS2, 8GB of RAM, and fast scratch disk (http://www.macgurus.com/forums/showpost.php?p=90956&postcount=47)

How much will Quad vs Dual-Core add up? or 12-16GB vs 8GB? And how much do all those small fractional steps save over the course of a project?

Photoshop CS2 Training DVD (http://www.barefeats.com/swc_cs2.html)

TZ
12-03-2005, 11:27 AM
Why I think more memory, and implementing some form of scratch disk (even using the boot drive scenario) and moving /Users to another drive, and installing a faster boot drive, are good for improving performance, and reducing the SBBOD.:


Jeff Schewe, Adobe Photoshop expert, offers us the facts on Photoshop, Jeff writes:

Read this: Photoshop CS2-How much RAM? ‹ Fact
http://photoshopnews.com/2005/04/04/photoshop-cs2-how-much-ram-fact/

When you get done and understand it, try reading:
Memory allocation and usage (Photoshop CS2)
http://www.adobe.com/support/techdocs/320005.html/

And then read:
Improve performance in Photoshop CS2 on computers with more than 1 GB RAM
http://www.adobe.com/support/techdocs/331372.html/

My two cents on the subject:

Memory: Try setting 50 percent (no higher than 75 percent) for anything less than 2 GB RAM.
Over 2.5 giga bytes of RAM:
The Mac OS limits all applications to maximum of 2 giga bytes of RAM. In other words, setting Photoshop's Memory setting to 100% will provide Photoshop with up to 2 GB memory, and leave the remaining 500 MB for the Operating System and other applications.

We do need to be careful to leave a cushion of unused RAM for whatever applications we run concurrently with Photoshop.

If we get a lot of OS 10's Spinning Beachball Color Wheel while using Photoshop, we probably need to install more RAM, or assign a lesser percentage of RAM to Photoshop.
Seeing the BeachBall is normal for working on very large files (over 200 mega bytes) while Photoshop's ScratchDisks gballard.net (http://www.gballard.net/psd/raid.html) catch up.

With over 3 giga bytes of installed RAM, I would start with a 100‹percent Memory setting in Photoshop.

NOTE: Adobe is recommending the Ram/Memory issues for 2.5GB-plus work stations...if 100% Memory is not working optimally, as recommended above, try reducing down to a "safer" 75%, said Adobe's Chris Cox.

Cache Levels: Adobe is recommending setting this to 4 (for now because of an OS10.3.2/PS8.0 conflict). I generally set the Cache Level to 8 on newer machines, I recall CS2 is defaulting to 6.

http://www.gballard.net/psd/troubleshootpurgepsd.html


See also, Photoshop Performance Benchmark Test 2 (http://www.macgurus.com/forums/showthread.php?p=83824)

Boots
12-27-2006, 11:49 AM
I've been spending a bit of time over on Adobe's Photoshop CS3 beta forum (http://www.adobe.com/cfusion/webforums/forum/categories.cfm?catid=626&flcache=7115704). A number of Photoshop engineers and beta testers frequent this forum.

Some noteworthy items:

* PS CS3 is 32bit, not 64bit as some had hoped. Adobe determined the cost/benefit ratio was not yet worth compiling this version in 64bit. Their view is that for the time being, the scratch data-caching-in RAM-by the OS feature mostly equals the possible gain from a 64bit Photoshop being able to address huge amounts of RAM directly- especially since the Mac OS is not yet fully 64bit.

* PS CS3 will probably not leverage more powerful GPUs. The engineers are looking closely at actively using the graphics card as a computing resource, but so far, this has not yielded performance improvement. Apparently, the current cards are still not sufficiently advanced to make that a worthwhile approach with Photoshop:

"We are continually working with the GPU makers to improve their cards and drivers to address the needs of applications like Photoshop." -Chris Cox, Adobe Photoshop Engineer

This thread (http://www.adobe.com/cfusion/webforums/forum/messageview.cfm?forumid=72&catid=626&threadid=1223862&enterthread=y) is an interesting discussion of the topic. Core Image apparently is not of much use to Photoshop.

* Still no rotate-the canvas-on the fly feature. Many users are dissapointed and clamoring loudly for this long sought after feature- Corel Painter has had this for years. Tablet users would greatly benefit from such a feature. Don't think it'll make it into this iteration.

* In direct CS2 - CS3 speed comparisons on PPC machines, CS3 is faster than CS2 in about the same percentage that CS2 was faster than CS; not a huge performance gain like with native Intel instead of Rosetta- but steady and significant for sure.

TZ
12-31-2006, 02:15 PM
The real issue is that the code base is probably like most code bases—full of latent correctness bugs that don’t manifest themselves only because pointers and other scalar quantities happen to remain 32 bits. Recompile as a 64-bit application, and all those latent correctness bugs suddenly appear; code that worked fails when 32-bit pointers now occupy 64 bits, data structures suddenly are a different size, optimized loops that made assumptions about sizes now fail, plugins and their APIs break, etc.
64-bits for Photoshop and Leopard. (http://diglloyd.com/diglloyd/blog.html#20061225TalkingAroundTheProblem)

Apple changes OS X every 2 yrs now. And with the move to Intel that adds one more forced upgrade to the code base. Keeping up is not easy.

Photoshop user base would love to move up to better systems, and many are probably waiting for three things to converge: Mac Pro's with octa-cores, Leopard, and CS3+, oh, and FB-DIMMs to fall in price ;)

TZ
01-13-2007, 11:33 AM
Please hope over to Sample PshopTest Results for latest CS3 beta vs CS2 results (http://www.macgurus.com/forums/showpost.php?p=106200&postcount=68)

TZ
03-12-2007, 05:10 PM
MacIntouch: Adobe (http://www.macintouch.com/readerreports/applications/topic4118.html)

CS2 does not have all that many problems on Intel Macs except for Illustrator and Version Cue for most people, where the issues in Illsutrator can be worked around and VC is not compatible at all and should not even be tried to be installed.

I work on on an Intel iMac at home since June last year, with CS2, and on an Intel MacBook since about two weeks back at work, with CS2. We (the newspaper where I work) have by now a couple of hundred of people with Intel Macs and CS2 but very few of those have any problems at all with the combination.

http://www.adobeforums.com/cgi-bin/webx/.3bc33165

For most people all CS2 apps work reasonably well if the system is OK, the fonts are OK and if you don't have any fancy additions to your system. Granted there are certain things that work less well, but most are able to work around them.

if you don't have anough RAM, do not run Photoshop at the same time as Illustrator if you are on an Intel machine. Also take up the habit of sometimes restarting your machine - that is often enough to make non-Intel apps come alive again.

frederick - 4:57am Mar 10, 07 PST

I have the new Mac Book Pro 2.2 with 2.33 GHz processor, 3 gb of ram and a 180 gb drive. I have worked as a graphic designer for 15 years. I have used Macs for most of that time.

The problems with CS2 did not start when I purchased this laptop (an upgrade from the original Titanium). It has been unraveling slowly since February

We've got a couple of hundred MacBooks and Mac Book Pros at the newspaper where I work (I work at the Mac Helpdesk and install and configure the machines and give user-support all days and nights), all with CS2 on them. None has actually had any particular problem except the known one with Illustrator Pathfinder, and some with saving to servers from Photoshop and Illustrator. An occassional freeze where a restart of machine has always helped. A few reinstalls and a few deleting of prefs. Actually very little compared to the number of machines and users we are handling. I personally run CS2 apps on 2 Intel Macs (MacBook and Intel iMac) and have only had minor porblems that could be worked around.

If it starts "suddenly" without you adding anything or doing anything in particular to the machine, I would suspect a damaged font or fonts or damaged prefs. Both could be caused by crashes.

http://www.adobeforums.com/cgi-bin/webx/.3bc34cef

Claims have shown that dropping the OSX back to 10.4.7 on an Intel will reduce crashing etc... The problem seems to lie within the OSX upgrade to 10.4.8.
(Some also blame an Apple Security Update.)


David Creamer - 5:37am Jan 20, 07 PST

There is what I know about problems:


There are some install issues, but I believe this has been resolved with newer packages--however if you purchase an older one, there is a fix on Adobe's site.

DO NOT install Version Cue--it will bomb your Intel Mac at start up.

There is an issue with the Pathfinder palette in Illustrator.

There are some harmless decimal display issues in some dialog boxes in InDesign.

All the programs will appear slower if coming from a G5 Mac; if from a G4, they will be about the same (depending on RAM); if from a G3, you will be faster.

Other than that, it works well. I see a lot of posts about about constant bombing when starting the program, or that multiple programs can't be open at once. I've experienced none of that. I believe this is mainly due to font problems and/or low RAM.

Here is what I would do on a new Mac:

Install as much RAM as possible--Rosetta likes RAM. Get your fonts under control (I have a PDF on OS X font management under the Download & Tip section of my website--plus some Photoshop speed tests). Clean our your font caches when having problems (I use FontNuke).

Illustrator CS2 crashes in the background (randomly) when using any other program.

Try closing the tab 'Open Type' and set both scratch disks to your hard drive.

Previously we had only the primary scratch disk set to the hard drive and the secondary set to none.
Don't know if this will work for you but we've not crashed since making these two changes with over a week now of intense use and having multiple programs running simultaneously. It used to crash many times a day.
http://www.adobeforums.com/cgi-bin/webx/.3bc27eb5

Installation troubleshooting
http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=329590

Illustrator CS2 crashing on Intel Based Mac
http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=333449

Many people probably know that the Pathfinder functions crash Illustrator CS2 on Intel Macs running 10.4.8. This fix originally comes from a guy called Mordy Golding (author of "Real World Illustrator CS2"). I have no connection with him, other than this tip really saved me a load of trouble!!!

Open Illustrator.
Close the "Appearance/Graphic styles" tool panel.
Restart Illustrator.
Pathfinder tools should now work.

After doing this, you can reopen the "Appearance/Graphic styles" tool panel and the crashes don't seem to return.
http://www.macintouch.com/readerreports/applications/topic4118.html

The Appearance palette is always open. I run CS2 on a 3 GHz Mac Pro, 5 gibibytes RAM, dual 30" ACDs, and they all run faster than they ever did on my dual 2 GHz G5.
http://www.adobe.com/support/techdocs/333449.html

TZ
03-18-2007, 10:30 AM
Adobe articles on optimizing performance:

#326405 Optimize performance in Illustrator (CS-CS2 on Mac OS X) (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=326405)
#332270 Optimize performance in Photoshop (CS2 on Mac OS) (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=332270)
#332271 Optimize performance of Photoshop (CS2 on Windows) (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=332271)
#319471 Troubleshoot installation problems (InCopy CS, CS2 (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=319471)

TZ
03-18-2007, 10:36 AM
#326405 Optimize performance in Illustrator (CS-CS2 on Mac OS X) (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=326405)
#332270 Optimize performance in Photoshop (CS2 on Mac OS) (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=332270)
#332271 Optimize performance of Photoshop (CS2 on Windows) (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=332271)
#319471 Troubleshoot installation problems (InCopy CS, CS2 (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=319471)

TZ
03-21-2007, 04:35 PM
By AppleInsider Staff (news@appleinsider.com)

Published: 02:00 PM EST Apple Inc. and Adobe Systems Inc. are reportedly working behind the scenes to improve the performance of Adobe's Photoshop under Apple's next-generation Leopard operating system.

<table align="right" border="0" cellpadding="5" cellspacing="5"> <tbody><tr> <td>
<!-- BEGIN: AdSolution-Website-Tag 4.3 : AppleInsider / News Rectangle Dynamic --> <script language="javascript" type="text/javascript"> Ads_kid=0;Ads_bid=0;Ads_xl=0;Ads_yl=0;Ads_xp='';Ad s_yp='';Ads_xp1='';Ads_yp1='';Ads_opt=0;Ads_wrd='[KeyWord]';Ads_par='';Ads_cnturl=''; </script> <script type="text/javascript" language="javascript" src="http://a.as-us.falkag.net/dat/cjf/00/16/23/56.js"></script> <!-- END:AdSolution-Tag 4.3 -->
</td></tr></tbody> </table> Adobe's Russell Williams explained (http://www.crn.com/software/197700697) how the integration of Photoshop with Leopard, due out a bit later this spring, will overcome an existing barrier to performance in the current version of the Mac OS X.

"Buffering is disabled by default in CS3 (Creative Suite 3) when running on Tiger because of an OS issue. Every 30 seconds, the OS pauses Photoshop for anywhere from a fraction of a second to several seconds as it manages that giant buffer cache," he wrote.

"If you're painting, this is a big problem, and it's why we made the 'disable VM buffering' plugin available for CS2. Apple says that issue is fixed in Leopard, but we haven't verified that yet."

In his post, Williams said Adobe's current plan for Photoshop CS3 is to enable VM buffering for big RAM machines running Leopard and disable it for Tiger. "But we'll provide an 'enable VM buffering' plugin to override this on Tiger if you don't mind the Tiger pause," he added.

TZ
04-30-2007, 08:33 AM
BAREFEATS:

OUR CONCLUSION FROM TEST RESULTS ON THIS PAGE (and others)
In spite of the limitations posed by the memory bus and OS X "Tiger's" handling of core swapping, there are things that the 8-core Mac Pro does signficantly faster than the 4-core Mac Pro. If you are using After Effects CS3 (or any app like it that knows how to use all 8 cores effectively), the 8-core is worth the extra money, in our opinion.

And if you perform multiple tasks within an application (like our QuickTime simultaneous conversion test above) or have multiple apps active (like in our Multi-Processing page), then you are a candidate for an 8-core Mac Pro.

INSIGHTS & RECOMMENDATIONS
We think it's awsome what Adobe had done to upgrade and refine After Effects CS3 so that it takes full advantage of all the cores (and all the memory) available in each Mac (both PPC and Intel). It's truly one of those applications that can sell hardware.

http://www.barefeats.com/octopro1.html
http://www.barefeats.com/octopro4.html

TZ
05-06-2007, 08:43 AM
Adobe Support. Check out this TechNote:

Manually Remove Photoshop CS3 public beta (Mac OS X). There are some obscure folders in the root Library/Application Support/Adobe folder that need to be deleted. Follow that TechNote and CS3 should install as intended.

Adobe Tech Note kb401502 (http://www.adobe.com/cfusion/knowledgebase/index.cfm?event=view&id=KC.kb401502&extid=kb401502)

TZ
05-18-2007, 05:22 AM
Looks like more cores isn't going to help CS3 and the memory bandwidth issues.

What's the story with Photoshop & multi-core? (http://blogs.adobe.com/jnack/2006/12/photoshop_and_multicore.html)

"... not all operations can or should be split among multiple cores, as doing so can actually make them slower.

Because memory bandwidth hasn't kept pace with CPU speed (see Scott Byer's 64-bit article for more info), the cost of moving data to and from each CPU can be significant.

Russell Williams, "The workers run out of materials & end up standing around."

The memory bottleneck means that multi-core can't make everything faster, and we'll need to think about doing new kinds of processing specifically geared towards heavy computing/low memory usage."

Complex video and audio signal processing are good examples of these kinds of tasks. And we're always looking for more useful things that Photoshop can do that are more computationally intensive.

MacWorld: Multi-Core Computing (http://www.macworld.com/2006/12/features/trends1/index.php)
64-bit Computing for Photoshop? (http://blogs.adobe.com/scottbyer/2006/12/64_bitswhen.html)

Boots
08-10-2007, 08:01 AM
I've just taken delivery of a MacPro 8 core machine which will be used only for intensive Photoshop. I have read Macgurus Photoshop Acceleration pdfs which seem to apply to G5 and earlier machines.

This forum has some tips about hard drive config for ultimate Photoshop usage however there is nothing relating to MacPro 8 core.

The PS Acceleration pdf and tips here apply to an 8-core MP just as much as to a G4 or a G5. The same principles apply:

1. use the fastest multi-processor available

In your case an 8-core- though your benefit from an 8-core versus 4-core will be marginal with the present state of Mac OSX multi-threading. PS will use in some operations but not all- close to 100% of each core up to 4 cores but you won't see 6 or 800% usage; an 8-core is currently overkill for Photoshop. It shines with multiple Apple Pro apps and some other Adobe apps running at the same time. But perhaps like you, I'm hoping the software will catch up with the hardware with Leopard..

2. install large quantities of RAM

You are well on your way there. But plan on using Activity Monitor during your typical work session to monitor page-swapping. This will tell you if you have adequate RAM for your workflow on average.
This is an area where the hardware needs to catch up with it's potential. Currently RAM I/O is bottlenecked apparently by the controller. This can be compensated for to an extent by using ( a lot of) the fastest possible RAM and proper config inside the box. I believe the 4GB modules are faster than the 2GB modules..

The extra RAM above 4GB is only really useful to you if you plan to enable the ForceVMBuffering plugin. You may (or may not) find as a result some interference with painting because of Tiger's vm 'pause' bug which hopefully will be fixed with Leopard. But in general you will get faster performance allowing the OS to cache Photoshop scratch disk data in RAM ("force virtual memory buffering").

3. install at least 2 fast hard drives, one for the system and one for PS scratch

From the latest data, it appears the new WD 750GB SATAII drive is every bit as fast as the 150GB Raptor, plus you get substantially more disk space. 4 of these sounds like a good choice but remember not to fill 'em up beyond 50% or so.

You omit a critical piece of info: how much "working" data do you currently have? Nowadays for pro digital photographers, it's every bit about file management as it is about optimizing hardware acceleration.

Because you plan to back up daily (right?) to massive external storage, you could get away with hosting your working files on a striped RAID0 of two internal SATA drives. This would give an advantage of faster Open and Save performance by virtue of the "working file" being on a separate really fast drive from the OS and PS. With the "working files" being off the system drive, that more or less eliminates any advantage or need to striping the system volume with 2 or more drives...

I see the concept and use (born out by my personal experience) of a striped system volume as most advantageous if the "working files" are on it, where they can benefit by the faster Open and Save performance, and also the faster OS virtual memory page-swapping performance when all installed RAM gets used up- which sometimes happens with really big image file work or huge file transfers.

Now my guess from your description is that the majority of your workflow is with images well under 1GB, perhaps most in the <250MB range. If this is the case, a single dedicated drive for Photoshop scratch should suffice nicely most of the time.

Therefore a safe reliable high-performance setup for you is:

Drive A (a single WD 750): Startup disk includes System, Library, Applications, Users
Drive B and C: (2 x WD 750s striped as RAID0) contains all image files
Drive D: a single WD 750 contains Photoshop scratch file. Assuming you use Bridge, you may also want to consider pointing Bridge's cache file ("use centralized location") to this drive for faster thumbnail building.

Several additional items to consider:

1. Using a mirrored external backup is probably a waste of space and an unnecessary risk. I can see using SoftRAID's mirror for rotating an offsite member but in general, if you have a software problem on the mirror drive, the corruption will instantly spread to the other drive in the mirror. Unless for some reason you really need a mirror, better to format as standard volumes; you get more space as a result and less potential for problems.

2. If using the suggested setup above, I would consider utilizing the space a little more efficiently by partitioning as follows:

Drive A first volume (60GB): System, Library, Applications, Users
Drive A second volume (600+GB): backup of image files on Drives B & C
Drive B & C (1200+GB): striped RAID0 single volume containing all image files
Drive D first volume (60GB): Photoshop scratch and possibly Bridge centralized cache
Drive D second volume (600+GB): backup of system volume on Drive A first volume and possibly second backup of image files on Drives B & C

Partitioning is not a liability in this case because the "second" volumes are not actively used; they function as passive storage. And when they are used when copying for backup, it's Drive A to Drive D or Drives B & C to Drive A or D- not Drive A to Drive A etc. In otherwords minimal disk-head thrashing when used..

----
Latest Photoshop Test:
http://www.macgurus.com/forums/showthread.php?t=20218