Speeding up Photoshop with a Scratch Partition

I’ve been thinking a lot about computer performance lately, as I start to but up against the limitations of my no-longer-new 2nd Gen MacBook. Increasingly, I’m finding longer load times for PSDs, more system hangs when switching between apps, and a general sluggishness that has started to sap my productivity (and sanity!). I had a sneaking suspicion that Photoshop was to blame for my woes, and this weekend, I decided that something must be done.

You probably already know this, but just in case, here’s a little background: You know those 2 little numbers at the bottom of your Photoshop canvas? They look something like a fraction, along the lines of 3.31M/212.9M? Those two sizes are your file size and (drumroll) working file size! The second, larger one is how much space your PSD is actually taking up while you have it open, even though it compresses down to the smaller one when not in use. A big part of this is that while working, each layer gets cached as a full canvas. The result, when you add up all your other open apps to the amount of RAM Photoshop needs, and then tack on all your layers, effects, masks and adjustments, you’ve probably got way more data than the amount of memory your system likes to keep active at any given time. What this all means is that Photoshop needs to write some of the extra data to your hard drive in order to be stable. Disk space is cheap and plentiful, and using it for memory is the easy thing to do, so easy that even your OS does it —a lot. As I write this, my laptop has 94 Gigabytes of stuff written down to VM.

In Photoshop, Virtual Memory is called “scratch space,” and as it competes with your system, you may start to see frustrating bottlenecks and crashes. This can be compounded if your disk data is fragmented, and both PS and your system are competing for read cycles and have to seek all over the disk to find what they need.

Thankfully, there’s an easy solution, and people in the graphic design and video production industries have been doing it for years—just create a second partition on your hard drive to dedicate to Photoshop, so system VM and scratch data don’t get intermingled! If you are lucky enough to have a 2nd hard drive, it’s easy—and better—to just use that, but if not, this is a simple how-to on partitioning your startup disk for Mac users. Your mileage may vary on Windows, but the process will be incredibly similar, just with different tools.

Step 1: Boot up from your Leopard Install CD

It’s necessary when altering the partition map of a disk to boot from another drive, so that changes the OS makes to the file system don’t screw up the process and force it to start all over again. This wisdom holds true as well for defragmenting, if you’ve ever tried to use a computer while defragging it, you know what I mean! Your Leopard disk has a few useful tools on-board, just pop it in the drive, restart, and hold the ‘c’ key as the system comes back up. This will tell your Mac to boot from any external drives, including your CD-ROM.

Step 2: Launch Disk Utility

Once the install screen is up, ignore it and select ‘Disk Utility’ from the ‘Utilities’ menu. In the sidebar on the left of the disk utility app you should see a menu of all your disks, with the existing volumes on each listed as sub-menu items. We are going to create a second volume in-line with Macintosh HD.

Step 3: Create your partition

To do this, select the parent drive for your main hard disk and then choose the partition tab to the right. There is a diagram called ‘Volume Scheme’ that shows the disk’s volumes, and their used space. You want to make sure you’ve got enough free space to get a decent-sized partition, with at least 6-10 gigs left over… anything less and performance will really suffer—and probably already is. If so, it might be time to start deleting files! For conventional use, a partition of 10 -15 gigs should be more than enough, meaning you want about 20-25 gigs of free space. Select your startup disk by clicking on it, then click the plus at the bottom of the Volume Scheme. Your diagram will split into two panes, the bottom one being the new scratch volume. Select it, give it a name (something that says what it is, like ‘Scratch’) and a size, then tab out of the last input before clicking apply to get around an annoying bug in the application.

Step 4: Update your Photoshop preferences

After a (hopefully) short time, your new disk will be good to go. All that’s left is to open up Photoshop preferences (the performance submenu) Check your new drive, and then uncheck the startup drive.

That’s it! Photoshop—and your whole system—will thank you, and your hard drive might even last longer!