Photoshop: How much does a dedicated scratch disk help?

[indigoflowAS]

I have an external drive here, 60GB...mostly empty w/ some files. I use it as a scratch disk for PS and Illustrator...how much does it improve performance, especially w/ the slowness of PS on the Intel right now. Thanks

 

[baleensavage]

I can tell you from my experience that a dedicated scratch disk has helped me immensly. I have an eMac with 40 gb hard drive which in todays world is nothing. However, replacing the hard drive in an eMac requires discharching the CRT which I simply won't do (I don't want to blow myself up). Anyway, I originally had my boot drive as a scratch disk, but since over 50% of that disk was full Photoshop was very very sluggish and bombed all the time on complex filters. I switched the scratch disk to an external USB 2 drive and it works great. I use the drive for other stuff but theres at last 150 GB free on it, which is plenty of room for photoshop to play.

On the other side of the equation, my G5 at work has a 150 GB drive in it and I wouldn't bother set up a secondary scratch disk because there's plenty of free space and an internal drive is much faster than an external drive.

So I guess my recommendation would be, if you break the 50% mark on your internal hard drive or if your internal hard drive is really small, set up a dedicated scratch disk. Otherwise, the performance boost won't be that huge.