Size of Scratch Disk?

[iii]

What would be a good size for a photoshop Scratch Disk? I'll be setting up my new computer tomorrow (OSX) and it has 3 Hard Drives.. I plan to have it set up like this

HD1 (SSD): Boot/Applications
HD2 (1TB): Data/Music
HD3 (640GB): Scratch Disk Partition or full HD for Scratch Disk?

If HD3's Scratch Disk is fine as a partition, I'll partition it 3 times for a Windows Operatin System, Time Machine, and a Scratch Disk.. is there a problem with using this drive like this for the scratch disk?

[evilagram]

No problem to my knowledge, just I think using such a large drive might be a bit excessive. All that necessary is a drive that photoshop can write to, meaning it has to be in a format OSX can read and write to, and that photoshop has permission to modify. As long as you can save and edit pictures at the location the scratch disk is, it should work fine.

I'd say the same principles apply to the RAM swap file, but I'm not sure how the principle holds for a Mac.

[Portus]

You should use a separate internal HDD for the scratch disk, other than that go for the fastest one possible.

[JaymeNYC]

what size is a good size for a scratch disk?

[Portus]

WD740HLFS

[Gardain]

what size is a good size for a scratch disk?

Let me put it this way.
The bigger and more extensively you work on your projects the more scracth disk youll need.
As such that ive recently worked on a project that was 14.000 px to 8.000 px and 400 dpi with around 40 to 90 layers.
it required around 15.gb of hdd

Just to be on the safe side - make it 20. gb.
And format the partion once a month.

If you are not working on big projects as such - 15 to 10 gb would be enough.

Ps: Photoshops scratch disk should be apart from the windows installed partion.