Scratch disk?

S

safehaven

Limp Gawd
Joined
Apr 28, 2008
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I am currently running 3X250GB WD2500JS 7200RPM in a RAID5 array. I have been reading on a photo forum that a lot of people use a scratch disk for Photoshop. So I came here to research it. The responses when people ask really seem to be mixed as to whether they are worth it or not. So, I have a few questions. If the answer to the first question is "no", then the rest can be disregarded.

Are scratch disks worth it? I really have no interest in moving my OS to another drive. So if I add a disk(s), it would only be for the purpose of a scratch disk.

Is a single disk OK for a scratch disk, or do you really need to stripe two or more disks?

Will standard 7200RPM disk(s) be sufficient, or are Raptors really needed?

Is it possible to run a RAID5 and a RAID0 on the same controller? (My mobo will handle at least 2 more drives, maybe more)

Is there something else I should consider?

Thanks for the help!
 
How much memory do you have and what size of Photoshop files are you dealing with?

In most cases, your best bet would be to upgrade your memory, or up the % Photoshop is allowed to use (in Photoshop preferences).

The scratch disk is only used if Photoshop uses all of it's allowed percentage of your total memory.

If you already have a ton of memory or don't want to upgrade your memory, Raid0 with two newer 7200rpm drives should be sufficient. You could always search around for Raid0 vs Raptor benchmarks. With a scratch disk, you'd benefit from lower seek times, and both higher read and write speeds. So Raid0 Raptors would be blazing fast but probably not very cost effective.

But having the max memory supported by your OS/Motherboard should be your first choice unless you have extra drives laying around.

And I believe most controllers (if not all) support multiple raid arrays.
 
I have 2X2GB of 1000MHz DDR2 on XP32, so I am tapped out on memory. My system shows 3.5 GB available. I have not really noticed any performance issue, but I also haven't run anything fast than what I have now. So, I really have nothing to compare to. My file sizes start out at about 10MB RAW files and get as big as 100MB psd files. If it matters in the decision, I dabble a very small amount in video encoding. I will have to check how much memory is allocated to PS. How much memory can I give PS without the rest of my system suffering?

Thanks.
 
Since you have 4GB of memory I'd say it'd be safe to leave Windows and everything with 768MB to 1GB of memory and let Photoshop use 75% of your total Memory.

In Photoshop CS3, it's under Edit > Preferences > Performance
and adjust the slider so it's using about 75%.

Play around with that, doing some usual editing for a while with your RAW photos and just stress it as you usually would, then with the files still open, Ctrl+Alt+Del, click on the "Processes" tab, then click on "View" and "Select Columns", then check "Peak Mem Usage" and click "OK".
Find "Photoshop.exe" in the list and check what it's Peak Mem Usage is.
That is the total amount of Memory it has used. If it's pretty close to the total amount of memory that you allowed Photoshop to use, then it's most likely using the scratch disk file.

If it seems like Photoshop is responding slowly after you've been using it for a while and just seems overall a bit sluggish while performing actions, then yes, another hard drive or two in a raid0 striped array for the designated scratch disk should speed things up a bit.

I do a lot of RAW photo editing myself along with editing of large 300MB+ Photoshop files and I only have 2GB of total memory, I let Photoshop use 75% of it, and it doesn't seem to use the scratch disk all that often, and when it does, it isn't noticeably slower, and I have it set to use one of my other hard drives (used for my music collection) as a scratch disk, so nothing fancy. And it's just an old 250GB 7200rpm drive.
 
Thanks for the help. Great info! I loaded up a few RAWs and a few PSDs and I was coming no where near the 1293MB that I have allocated at 75% usage in PS. So, I don't think I need to worry about a scratch disk.
 
Yup, no problem.

A year or so ago, I had the same question and had a very tough time finding an answer that was particular to my setup/usage. So I'm happy to help ya out.
 
one of the best ways to see if photoshop is going to disk is to right-click on the bottom left corner (where there is the little black triangle) and choose "efficiency". When this drops below 100%, you're starting to go to disk instead of staying in memory. When I was using a xp 32-bit, I had 2GB of memory, used 2x160GB for my C:, 2x80GB for my scratch disk, and it worked very very well.
 
Another great tip, thanks! I gave that a try too. I loaded up a few PSDs and RAWs again. I did not have any efficiency issues until I ran the Molten Lead action a couple of times and purposely tried to stress the memory. It maxed out the memory way quicker than I expected it to. I dipped down to 16% efficiency. OUCH. I absolutely never use that action so I am thinking that I should be OK.
 
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