By default CrashPlan PRO backs up everything in the User directory. Sometimes there are some files stored there that it doesn’t make sense to back up and there is no reason to expend any CPU or disk on backing them up.
iTunes Movie Rental Backup Problem
Let’s look at iTunes movie rentals. An iTunes movie rental file is a 1-2GB file that gets automatically deleted after 24 hours. If you back it up it won’t play after 24 hours anyway. Basically it’s a waste of time to back up. So we’ve made sure you can tell CrashPlan PRO to exclude entire file types from backing up.
Metadata to the Rescue
iTunes attaches metadata that says “Don’t back me up” to each movie rental file. CrashPlan PRO is smart enough to note the request and ignore the file.
Any program on OS X can tag any file with the “Don’t back this up” metadata. Another example of this would be VMware a product that lets you run Windows on Mac. The virtual disk file “vmdk” is tagged with “Don’t back this up” and we honor that request.
But what if you don’t agree with VMware and you want to back up that VMware image?
What Is Being Excluded?
Finding out what is excluded from backup due to metadata is easy but requires interaction with the OS X command line. Enter the following line in Terminal to find out which files are being excluded on your system:
sudo mdfind "com_apple_backup_excludeItem = 'com.apple.backupd'"
Here is the result of the above command on my MacBook:
MacBook:~ [user]$ sudo mdfind “com_apple_backup_excludeItem = ‘com.apple.backupd'”
/Users/[user]/Music/iTunes/iTunes Music Library.xml
/Users/[user]/Pictures/iPhoto Library/iPod Photo Cache
/Users/[user]/Library/iTunes/iPhone Software Updates
The above command queries spotlight to tell you every file that has the metadata “com_apple_backup_excludeItem” which means “Don’t back this up.”
Removing Exclusion Metadata
In my case I agreed with the developers in all but one case: my Windows Vista virtual disk called “windowsvista.vmdk” located in the “windowsvista” folder. Here is how to remove the metadata on this file to make sure it will be backed up by CrashPlan:
xattr -d com.apple.metadata:com_apple_backup_excludeItem windowsvista.vmdk
#This removes the meta data from vmdk file
sudo mdfind “com_apple_backup_excludeItem = ‘com.apple.backupd'”
#Check again to make sure it’s gone
Now CrashPlan is backing up my windows vista disk. If I was running TimeMachine it would also back up the vmdk file over and over again quickly filling up my destination drive. CrashPlan doesn’t suffer from this issue as it knows which parts of the file changed and only sends those. This explains why VMware excluded their disk image from backup and I suspect there are other programs out there that do so as well.
It is wise to make sure your critical files are not marked with metadata that says “Don’t back me up!”