I just had a little chat about this with a colleague who does much heavier Photoshop lifting than I do (layered medium format scans) and he concurred that—with contemporary Mac Pros and drives like the ST31000340NS—no special efforts are needed for the PS scratch disk.
Even with gargantuan layered files, Photoshop is going to be limited by the overhead of its virtual memory architecture, not by the underlying storage system. (No matter how fast your disk sub-system, when working with huge files, you have to try to minimize the burden on PS by keeping only one file open, keeping the undo history fairly shallow, etc.)
A Mac Pro with ample RAM and a few ST31000340NS drives and no RAID whatsoever is going to be a highly responsive computer for most any Photoshop work. Really, the RAID options in this context are only attractive for mirroring drives. Mirroring only protects against drive failure. Personally, I'd rather have Time Machine than mirroring, because Time Machine gives me a degree of protection from user error in addition to protection from drive failure. Other people will have different priorities. If the OP doesn't feel Time Machine is a good match for him, then I suppose I'd look to RAID 5, which is more space efficient than RAID 1 or 0+1. I suppose that I'd also view the RAID card from Apple as attractive (despite the price) simply because it's probably the easiest way to set up serious RAID on a Mac Pro. In understand that getting OS X happily installed on a RAID system can be a real headache with third party solutions.
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
At the moment my PC is a Dual opteron with 2 power supplies and 3 x 75gig raptors and 5 x 400gig drives. 2 of the raptors are mirrored for the operating system, drive 3 (raptor) is for the scratch disk and the balance of the 5 x 400gig drives are for Data.
It runs exceptionally fast but tends to be a bit noisy though. Now my problem here is redundancy and I have to back uip all those files in my 5 x 400gig drives and thats the reason why I am interested in raid configuration.
My other solution could be this
1. Drive 1 - used for operating system plus working files and just use the 320 gig drive that comes with the mac pro
2. Drive 2 - Working files and scratch disk (purchase a 150 gig raptor or even a 500 gig drive for working files and I can back that up with external drive)
3. Drive 3 & 4 Mirror them and used strickly for data storage.
4. I will then keep my 2 spare 1 TB drives as emergency backup or when drive 3 & 4 becomes full, I will just replace them with my 2 spare drives.
Now using this formula, I presume apple operating system would have built in software to mirror drive 3 & 4 and as such I will save over $1000 on the raid card. If I use drive 3 & 4 strickly as data directory I would not require speed and I reckon software mirroring would be sufficient
Perry
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
"When you run Photoshop CS3 on a 64-bit operating system, such as Mac OS X v10.4 and later, Photoshop can access up to 8 GB of RAM. You can see the actual amount of RAM Photoshop can use in the Let Photoshop Use number when you set the Let Photoshop Use slider in the Performance 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, and actions. If you have more than 4 GB (to 8 GB), 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 increase performance of Photoshop."
My MacPro is configured with 12 gigs of ram, 500 GB WD hard drive for Programs, 500 GB WD hard drive for scratch disk, 1 TB Barracuda for Time Machine back up and 1 TB Barracuda for image storage.
Jerry
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
Last edited by Jerry Skrocki; 04-25-2008 at 06:44 PM.
Jerry: are we sure there's really much value at this point to dedicating an entire drive for scratch? I'm skeptical.
Perry: yes, you can configure OS X to mirror data, but I believe writes to software-mirrored volumes take exactly twice as long. I take a little issue with your use of the term "backup" with regard to mirroring; it makes me unsure what exactly you're trying to accomplish. Mirroring is not backing up. Mirroring is redundancy against drive failure. If you write crap to mirrored drives, you have two copies of crap, and if you delete something accidentally, you still don't have it any more, because it's deleted from both drives. I suggest you re-examine the approach of foregoing mirroring and instead turning to Time Machine to provide a transparent working backup. Since Time Machine goes on its own physical drive, you get your drive failure protection that way. Time Machine would keep your system drive and "work" drive backed up, but that wouldn't solve all your data management problems, which appear to extend to archiving a pile of data. Perhaps you should move your archives out of the box and into NAS (RAID 5 or 6) or a Drobo?
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
Jerry: are we sure there's really much value at this point to dedicating an entire drive for scratch? I'm skeptical.
You don't need an entire drive for scratch but you do need a drive that is separate from your operating system for optimal performance.
Again from the Adobe Tech note:
"A scratch disk in Photoshop is similar to virtual memory in Mac OS. For the best performance, you should set the primary scratch disk to a defragmented hard drive that is not running the operating system and that has plenty of unused space and fast read/write speeds (rather than a network drive or removable media such as a Zip drive). Photoshop requires at least 2 GB of free hard-disk space, but more is recommended. The OS volume should contain at least 20 GB of free space to ensure that the virtual memory system has plenty of available hard disk space. If you have more than one hard drive, it is suggested that you specify additional scratch disks. Note that RAID 0 partitions provide the best performance as Photoshop scratch disks. Photoshop CS3 supports up to 64 exabytes (EB) of scratch disk space on a total of four volumes. (An EB is equal to 1 billion gigabytes.)"
Jerry
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
Last edited by Jerry Skrocki; 04-25-2008 at 11:47 PM.
Linear Mode
