After installing the Backup client update (v10.0-18058 - released October 2011), incremental or differential backups are much larger than expected (4 - 5 times larger than before the client update).
There is an Acronis bug in this OEM client build which causes shadow copies to be incorrectly included in incremental or differential backups on some client machines when they should be skipped.
The problem will be resolved in the next release of Kaseya Backup which will include a new Acronis build. At the time of writing there is no release date for this. A workaround is to roll the Backup client back to the previous Acronis build (10.0-17552) using a set of custom agent procedures that have been created for this purpose. Here are the steps to achieve this: -
1) download the Acronis 10.0-17552 client install files from here
2) extract both files (AcronisTrueImageServer.msi and AcronisAgentWindows.mst) to the shared files directory on your Kaseya server (\Kaseya\WebPages\ManagedFiles\VSASharedFiles)
3) download the agent procedures from here
4) the archive contains two exported agent procedures (Procedure Remove Acronis 10.0-18058.xml and Procedure Install Acronis 10.0-17552.xml) - import them using Agent Procedures > Schedule/Create > Import Folder/Procedure
5) run the Remove Acronis 10.0-18058 procedure on the target backup agent
6) when complete, schedule a reboot
(!) reboot is required to remove Acronis low level drivers, otherwise installation of the "old" build will not be successful. You may choose to modify the procedure and add a reboot step at the end if you plan to run it at a time when reboot is possible.
7) run the Procedure Install Acronis 10.0-17552 procedure
8) when complete, go to Backup > Configure > Install/Remove and verify the installation - it should now report the version as 10.0-17552
Kaseya Backup client v10.0-18058