On 12/07/2011 01:05, Holger Parplies wrote:
>
> so, you're saying that you don't trust your file system, but you trust LVM to
> keep 4 snapshots accurate for up to four weeks? I think I understand Les'
> point (if he's making it) that a hardware-based "don't do anything" approach
> is more reliable than a software-based "accumulate the information needed to
> undo all my changes". But I also understand your point of "as long as it
> works, it gives me three previous states to go back to".
Take it as you like. I never said I don't trust my filesystem. At least
you have to trust *something* or you'll end up in endless layers of
security.

We both have the possibility to roll-back to a point some weeks ago. If
LVM doesn't work as expected *or* Less disks getting broken during the
swap- it's just the same.
> I'm just wondering whether you're unmounting the pool FS before the snapshot,
> or if you're relying on it to be in a consistent state by itself. How much
> testing have you done?
You can perform tests multiple times- every time they are fine but in
case of emergency something else fails you haven't thought of
previously. Meaning: There's no point in testing if a not properly
closed filesystem is able to recover as you can't forsee it in any case.
I'm using ext3 with data=journal, so it should work fine even without
proper unmounting.


>> The only thing I have to evaluate is to have the proper size of the
>> snapshot.
> Which, in itself, doesn't sound practical. Effectively, you are estimating
> how much new data your backups for a week (or four weeks?) will contain.

I have to estimate how much data changes on the volume for a weeks time,
yes. Then I take a snapshot. And another week. So it's a one week
estimate. And why should this be an issue? The secondary it a 2TB disk
while the original is around 1TB. So the amount of data changing within
a four weeks time frame can be 100%. This is fine. Although from
monitoring it the change rate per week is far below 100GB....

Greetings

Christian


------------------------------------------------------------------------------
All of the data generated in your IT infrastructure is seriously valuable.
Why? It contains a definitive record of application performance, security 
threats, fraudulent activity, and more. Splunk takes this data and makes 
sense of it. IT sense. And common sense.
http://p.sf.net/sfu/splunk-d2d-c2
_______________________________________________
BackupPC-users mailing list
BackupPC-users AT lists.sourceforge DOT net
List:    https://lists.sourceforge.net/lists/listinfo/backuppc-users
Wiki:    http://backuppc.wiki.sourceforge.net
Project: http://backuppc.sourceforge.net/