We love CrashPlan for its inexpensive, unlimited and automated backup service, but many of us have seen terrible upload speeds or high CPU usage when CrashPlan is running. This might be the fix you need.
Network Rockstar alter3d wrote of his issues using CrashPlan to back up all his things, but not getting very fast upload speeds despite his new zippy DSL line. The chart above shows the upload speed performance decline over time... until he found the solution, which was disabling CrashPlan's deduplication algorithm, which checks to make sure you're not backing up files previously backed up. In CrashPlan's advanced backup settings, the options are automatic, full or minimal. CrashPlan's support guide explains the differences:
Automatic - Full de-duplication is used when going over a slow Internet connection. Minimal is used when going direct to disk or over LAN.
Full - Every effort is made to identify duplicate data. While being 100% effective, it requires a great deal of CPU power. With this setting you're sacrificing CPU and speed to save bandwidth and disk at destination.
Minimal - Several methods are used to identify duplicate data. While about 90% effective, this setting requires far less CPU power and will speed up initial backup significantly, typically 400% on a single processor system.
It's clear that minimal would be the best option for most users who are concerned with CPU usage and upload time, as well as those with relatively fast internet connections, yet when I checked my settings, dedupe was set to full.
alter3d found that switching the settings in CrashPlan to minimal didn't make a difference, but altering a line in CrashPlan's XML configuration files did, so he's provided some easy scripts to fix that issue.
You could first try changing the dedupe setting in CrashPlan before using these scripts and seeing if they help. (Marco Arment found that turning off compression and setting deduplication to minimum worked very well for him and his Synology setup.) To see the speeds before and after your settings changes, double click the CrashPlan logo to access the hidden command line tool and download your logs.