Thursday, 9 June 2011

CrashPlan on Mac OS X

I've been testing CrashPlan as a method of backing up my files to the cloud. After taking a couple of weeks to get all the data up, it's working pretty well and I'm planning on paying for it on a monthly basis. The one downside is that having CrashPlan loaded appears to slow my old Core 2 Duo Mac Mini down. This seems to be because the Java app consumes several hundred megabytes over time.

CrashPlan comprises of two parts: The front end GUI and a Java-based engine. The first job I did was to customise the backup window so that it only backs up overnight. As my Mac is on all the time, this is not a problem. The reason for this is that I'm asleep and not using the computer, and my ISP, Plusnet, have a monthly bandwidth allowance, but 12am-8am traffic is not counted.

In order to work around the memory leak issue, I've created two root cron jobs to start up the engine just before it's needed, and shut it down again afterwards. To do this requires the UNIX command prompt (open the Terminal app):

First, open a root prompt by running a BASH shell:

$ sudo bash

(enter your password here)

Then edit the crontab by running:

# crontab -e

Enter the following lines:

# Start CrashPlan engine at 5 minutes to midnight in time for overnight run
55 23 * * * /bin/launchctl load /Library/LaunchDaemons/com.crashplan.engine.plist
# Stop CrashPlan engine at 5 minutes past 8am to free memory after overnight run
05 08 * * * /bin/launchctl unload /Library/LaunchDaemons/com.crashplan.engine.plist

Edit the vi editor (hit escape, then type :wq! and hit return).

You can view your crontab by running:

# crontab -l

This gives the benefit of overnight CrashPlan backups, but without having any unnecessary services running in the background during the day.

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