Disaster Recovery and Rsync (was [lug] Commercial rsync service?)

[Jeffrey Siegal]

On Feb 3, 2006, at 23:34 , Nate Duehr wrote:

>> One way do deal with this is to use LVM snapshots.  Snapshot,  
>> mount snapshot read only, rsync from snapshot, unmount and then  
>> delete the snapshot.
>
> This is very common in the commercial world.  There's another step  
> usually...
>
> Put DB in quiet mode. (No disk reads or writes, but DB is still up.)
> snapshot
> Put DB back in normal mode.

This isn't strictly necessary, but I guess it avoids a recovery step  
and the possibility of data loss due to bugs in the database and/or  
storage subsystem.  Ordinarily just creating a point-in-time snapshot  
should be sufficient, with database rollback/recovery doing  
everything else required.  The snapshot looks like the system  
suffered from a crash at that instant, which a decent database should  
be a able to deal with.

Be careful with non-transactional databases though (such as MySQL  
with non-transactional table types).