[DRBD-user] Tape backups (yes, again)

Ken Dechick kend at medent.com
Thu Jun 11 20:32:02 CEST 2009


Hello all,

  I know this has been discussed before, but I am still trying to "sell" the whole DRBD/Heartbeat system to the higher-ups within my company and I can't find a solid answer on this here in the mailing list. So I will ask again.

I NEED to have tape backups - we are in the medical software business and having a tape to fall back on is crucial to our business model (if a client's office burns to the ground and both the primary and secondary servers in the 2-node cluster are gone for good, then a tape backup no more than a day old stored offsite is the only solution left - no doctor will tolerate losing much more data than this).

So let's forget the whole mounting secondary as read-only mess for now. What I am thinking is this:

  -at backup time (2AM?):
    -stop drbd and heartbeat on the secondary
    -bring down the dedicated eth1 connection to the primary (leaving eth0 still up so I can get in if need be)
    -mount the sda4 partition (NOT the drbd0 device as drbd will be stopped) to it's normal position
    -run my usual tape backup routine
    -unmount sda4 again
    -bring eth1 back up
    -start drbd and heartbeat again

I am thinking that in this way my users will still see NO downtime of the primary resource (unless of course there is a hardware failure during the tape backup while the secondary is offline!), and I still get a tape backup that is quite current. Once the secondary comes back up again anything that may have changed during the backup will replicate leaving me with only a tiny window of time to be without the secondary (an hour or two tops for my tape backup to run).

Could it really be this simple? We don't use lvm at all, just plain old ext3 file systems, so I believe this negates the whole lvm snapshot and then back that up dicussion I have seen here in the lists. What are your thoughts? Currently we implement what we call a view-only backup server at some clients where a second server is up and running and sync'ed (using rsync) only once a night from the main, then a tape backup runs once the sync is done. In this way our aplpication is only offiline during the time it takes to complete the rsync. I am thinking that there is no need to do this at all if I have a DRBD/Heartbeat 2 node cluster. (I certainly don't need a 3rd machine and keep doing the rsync then tape like we do now do I??)

Thanks in advance for any thoughts on this you can share!

-Ken

Kenneth M DeChick
Linux Systems Administrator
Community Computer Service, Inc.
(315)-255-1751 ext154
http://www.medent.com
kend at medent.com
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