There's nothing worse than being half way through editing a photo using Photoshop when a message pops up saying. The Scratch Disk is Full. No explanation, no help. If you've spent a lot of time editing the photograph you're in a bit of a predicament, because you cannot do anything about the problem and will have to close the photo unsaved and start again. This is a waste of time, but a valuable lesson and one that will encourage you can do something in preparation for your next editing session.
The scratch disk is Photoshop's way of using your computer's virtual memory to run more memory intensive tasks. The program needs RAM he amount increase each upgrade) to run and when you start doing complex editing more RAM is used. At some point your computer will run out and it's then when the scratch disk kicks in. The system borrows memory from one of your computer's drives. If you only have one drive and you get the message it means you don't have enough free space. Many Photoshop users either partition a large capacity hard drive and allocate the empty partition for Photoshop or they buy a second internal or external drive for Photoshop. The latter option is the better one as Adobe recommend that The scratch disk should be on a different drive than the files you are editing.
Photoshop uses the hard drive that the operating system is installed on as the primary scratch disk by default. To allocate a different scratch disk you need to visit Photoshop's preferences: Edit > Preferences > Performance and set the disk that you want Photoshop to borrow RAM from. When you visit this palette you'll see that Photoshop has automatically detected any drives that it could use for the Scratch disk. It's up to you then to select the one you think is appropriate
Photoshop CS3 has a new improved window. You tick the disk/s you want to use and then click on the arrow to move the most important disk to the top. Earlier versions of Photoshop had a set of drop downs to select the disk and its order of priority. You could, for example, have three drives, two internal and an external. Simply allocate the one with the largest free space as the main scratch disk and the other two as secondary scratch disks.
Photoshop displays RAM and scratch disk usage and allocation in the Scratch Sizes section of the status bar at the bottom of your photo.
- Regularly run a disk defragmentation utility on the drive you use as the scratch disk to free up space.
- Set the preferences so the scratch disk size shows under the photo rather than the default file size.
- Buy more RAM for your PC to make sure it's maxed up.