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You’re Doing That Wrong is a journal of various successes and failures by Dan Sturm.

Managing Disk Cache (with a Hammer)

Throughout the course of a given project, I use a handful of applications to complete my work. At the moment, I edit in Avid MediaComposer and Final Cut Pro 7. I do my VFX work in NukeX. I review shots and conform sequences in Hiero. And I do final color correction in AfterEffects with Red Giant Colorista II. There’s an obvious advantage to using the right tool for the task at hand, but there’s a caveat that I almost never remember until it smacks me right in the face: disk space.

I’m not talking about the space required for digital negatives, plates, renders, or project files. No, the piece I always manage to forget is the massive disk cache each application in my workflow creates on my startup disk [1]. With single frames of a sequence ranging between 5 and 30Mb, and individual shot versions reaching well into double digits, disk cache can take up a ton of space. And since cache files are created whenever an element is changed and viewed, it’s not an easy task to estimate how much space will be used by a project ahead of time.

Most applications, including every application I use, have built in preferences designed to limit the size of the disk cache. Most also feature a big button labeled “Clear Disk Cache”. These preferences are great if you spend all your time in a single application, but are of little consolation when you’re halfway through previewing a shot in Nuke and OS X pops up telling you your startup disk is full. Once you’re in that sad, embarrassing moment, good luck getting AfterEffects to open so you can hit that “Clear Cache” button.

“To the Finder,” you say? Even if the Finder were responsive when your startup disk had less than 50Mb of free space, are you the kind of person that keeps a sticky note on your monitor listing the paths to all the buried, hidden cache folders for each application? Neither am I.

Historically, I’ve gone straight to my project’s Renders folder and deleted my 2 oldest exports, giving me about 6Gb of breathing room to go hunt down the various disk hogs. Not a great solution. What would be ideal is the ability to hit one keyboard shortcut, see a list of which applications are taking up space and, more importantly, how much space, then quickly purging the unnecessary files.

Normally, the sizes for AfterEffects, Nuke, and Hiero are in the double digits of Gigabytes. This screenshot was taken after using the script as intended.

The Script

cache.command: 

#!/bin/sh  

clear  
echo Current Cache Size:  
echo      
du -c -h -s "/Users/dansturm/Library/Preferences/Adobe/After Effects/11.0/Adobe After Effects Disk Cache - Dan’s MacBook Pro.noindex/" "/var/tmp/nuke-u501/" "/var/tmp/hiero/" "/Avid MediaFiles/MXF/" "/Users/dansturm/Documents/Final Cut Pro Documents"  

echo      
read -p "Purge Cache files?(y/n) " -n 1 -r  
echo      
if [[ $REPLY =~ ^[Yy]$ ]]  
then
    rm -r "/Users/dansturm/Library/Preferences/Adobe/After Effects/11.0/Adobe After Effects Disk Cache - Dan’s MacBook Pro.noindex/"*
    rm -r "/var/tmp/nuke-u501/"*
    rm -r "/var/tmp/hiero/"*
    echo    
    echo Done!
    echo      
fi

The script displays the space taken up by each application, the path to that cache folder, and a total of space used. It then prompts for a y/n input to delete the cache files.

Since managing Avid and Final Cut Pro media requires a bit more attention and nuance than a dumb hammer like this can provide, their disk usage is listed, but their files are not removed. If you modify the script to delete Avid of FCP media, allow me to preemptively say “I told you so” when your project becomes corrupted.

Details

I run the script with a FastScripts keyboard shortcut. I wanted to shortcut to open a new Terminal window to display the information, so the keybaord shortcut actually calls a second short script called cache.sh which takes care of that part: 

#!/bin/sh  

chmod +x /Path/To/cache.command; open /Path/To/cache.command

The paths for the cache folders are hard coded into the main script and, as I mentioned, not all items listed are deleted. I like to see as much information as possible, but manage the deletion list more carefully.

For me, the main offenders of disk cache consumption are AfterEffects and Nuke which, together, average nearly 200Gb of disk usage. Once I’ve dealt with those 2 applications, I don’t usually need to go hunting for more free space.

Next time I accidentally inevitably fill up my startup disk with cache files, it’ll take seconds to rectify, rather than a half hour of excruciatingly slow, manual effort.

Hooray for automation!

  1. While it’s true that, in almost every application, you can re-map the disk cache folder to any disk of your choice, the entire point of a disk cache is to have the fastest read/write speeds possible, and no disk I own is faster than my rMBP’s internal SSD.  ↩