What does it mean when I get the message "scratch disc is full"?

Trying to work on Photoshop and I'm getting the message, "scratch disc is full".

MacBook Pro, Mac OS X (10.6.8)

Posted on Nov 16, 2012 10:18 AM

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8 replies

Nov 16, 2012 11:37 AM in response to cec1976

When you edit pictures in Photoshop all the changes are stored in temporary files so that you can do multiple undos. If you have a lot of edits that can use a lot of disk space. The operating system also needs temporary space - the more applications you have running, the more it needs. As you work, keep a watch on your free space, and don't let it drop below about 20GB. If you can't manage that, you need to consider a bigger disk.


Anotther thing that eats disk space is the trash - if you delete a lot of pictures, for example, as you review the results of a day's shooting, they go to the trash but the disk space is not freed until you empty it.

Nov 16, 2012 12:10 PM in response to cec1976

As a temporary measure, quit Photoshop periodically. I don't know if you can tell Photoshop to use an external disk as temporary scratch space. Look at getting a bigger disk, or an external disk and moving some of your files across to it.


Some people have reported success with replacing their DVD drive with a hard disk - these have a capacity of about 1TB. You would then have the convenience of two internal disks, and use your DVD drive externally when needed.

Nov 16, 2012 12:41 PM in response to cec1976

Ultimately here is the deal. Like OS X and Windows do at the system level, Photoshop will grow a virtual memory scratch file on your hard drive if you don't have enough RAM to do what you are trying to do.


That means, step 1 in preventing the scratch file is to put more RAM in the Mac so that Photoshop doesn't run out so fast and have to shove data off to the disk to make room.


Step 2 is to put the scratch file on another disk. This is why pros have often used desktop towers, because you can put multiple disks inside them. For example, system on one disk with lots of free space, photo library on another disk so it can grow freely, and another disk that is used exclusively to hold scratch files for Photoshop and other programs that need to do the same thing like Apple Final Cut. Splitting the data streams (system, file access, scratch) like this also speeds up the machine considerably since they're not all trying to use the disk at the same time.


The way you put the scratch file on another disk is to go into the Photoshop prefs, click Performance, and assign one of your other disks as a Scratch Disk there. (Use a fast disk, not a network or USB 1.0/2.0 disk, and partitioning your main disk will not help.)


If you do this, you don't need to change your main disk at all, you don't need to manually move any files off of it. Because by moving the scratch file off your main disk, the 58GB of free space you have there will now be plenty.


I used to use a PowerBook with an external monitor as a Photoshop machine, and plugged in a FireWire 800 external as a scratch disk. Even just doing that helped a lot.

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What does it mean when I get the message "scratch disc is full"?

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