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

Jürgen Scholz juergen at kernkraft400.com
Fri Jun 12 12:08:09 CEST 2009


Hi!

>   -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)
No need for that. When drbd is stopped it doesn't matter if your  
replication link is up or not.

>     -mount the sda4 partition (NOT the drbd0 device as drbd will be  
> stopped) to it's normal position
Here is a crucial point. You should at least remount the filesystem on  
the primary read-only - to prevent your filesystem's metadata AND the  
actual data from being corrupted because you pulled the plug in the  
wrong moment.

>     -run my usual tape backup routine
>     -unmount sda4 again
>     -bring eth1 back up
see above
>     -start drbd and heartbeat again
This should work.

> 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.
Your assumtions seem to be correct to me.

> 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
I don't understand why you seem to insist on going the complicated way  
when you can have this which significantly lower downtime just by  
using lvm and snapshots. (disks <-> LVM <-> DRBD)
With using lvm on both ends you could even run your tape backup from  
the primary or the secondary (important if you have a hardware failure  
and can't replace the machine in less than one day) without modifying  
anything on your setup.

cheers,
  juergen



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