[rdiff-backup-users] Using --mirror-only to mirror an rdiff-backup dir

[Christopher Schanzle]

We're using rdiff-backup to back up our Cyrus mail spool for about 4500 
users (140 GB, 3.5 million files).  It's great, but since mail is 
important to some people, we want to make a second copy of the 
rdiff-backup directory in case the backup server barfs.  I tried using 
rsync, but it's memory requirements for 8 million files is at least 1.3 
GB (the second backup host has only 512MB...ouch!).  I don't want to 
break up the rsync into multiple subtasks since we have lots of hard 
links.  I could throw more hardware (RAM) at the problem, but...

I tried to use "rdiff-backup --mirror-only" of the rdiff-backup directory 
to another system.  But I cannot get it to mirror the rdiff-backup-data 
directory since it is automatically excluded!  I tried --including it, to 
no avail.  Any suggestions?

I noticed the release announcement for 0.11.1 -- Ben, please reconsider 
removing the --mirror-only option!  Rsync is not the perfect tool for 
mirroring large datasets!  Does anybody have any other suggestions?  And 
thanks again for all the effort put into rdiff-backup.

Chris Schanzle