[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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