[CentOS] CentOS Server Backup Options: at runlevel 5? ... w/snapshot

John R Pierce pierce at hogranch.com
Fri Mar 16 15:40:24 EDT 2012


On 03/16/12 11:53 AM, Les Mikesell wrote:
> LVM snapshots just present a view of the disk as it was when the
> snapshot was taken.  To do that, whenever you write to the disk with a
> snapshot active, it first copies the old data into the snapshot.
> Blocks that don't change don't need to be copied.    This doesn't do
> anything by itself to make the files consistent, but you might stop
> your apps momentarily, make the snapshot, then let them run again
> while the snapshot is being backed up.

one thing Microsoft did well in Windows NT...  the built in 'volume 
snapshot service' support, VSS... when you go to create one, the volume 
manager sends messages to all applications that have registered 
themselves with the VSS subsystem to quiesce their disk state before it 
creates the snapshot, then tells them to resume as soon as the snapshot 
is stable.   this is mainly of interest to database servers...



-- 
john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast



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