atom feed23 messages in com.redhat.linux-lvmRe: [linux-lvm] Using LVM Mirroring t...
FromSent OnAttachments
Ambrogio De LorenzoSep 16, 2009 6:59 am 
André GillibertSep 16, 2009 8:05 am 
Ambrogio De LorenzoSep 16, 2009 9:47 am 
Brian J. MurrellSep 16, 2009 9:58 am 
mala...@us.ibm.comSep 16, 2009 11:19 am 
Ambrogio De LorenzoSep 16, 2009 12:03 pm 
Ambrogio De LorenzoSep 16, 2009 12:15 pm 
Brian J. MurrellSep 16, 2009 12:49 pm 
André GillibertSep 16, 2009 1:03 pm 
Ambrogio De LorenzoSep 16, 2009 1:22 pm 
mala...@us.ibm.comSep 16, 2009 1:33 pm 
Kai Stian OlstadSep 16, 2009 3:03 pm 
Bryn M. ReevesSep 17, 2009 2:57 am 
Stuart D. GathmanSep 17, 2009 8:06 am 
Brian J. MurrellSep 17, 2009 8:34 am 
Stuart D. GathmanSep 17, 2009 3:49 pm 
Les MikesellSep 17, 2009 4:26 pm 
Brian J. MurrellSep 17, 2009 4:48 pm 
Stuart D. GathmanSep 17, 2009 5:57 pm 
Sven EschenbergSep 17, 2009 6:51 pm 
Stuart D. GathmanSep 17, 2009 6:55 pm 
Mark H. WoodSep 18, 2009 9:05 am 
Stuart D. GathmanSep 18, 2009 12:12 pm 
Subject:Re: [linux-lvm] Using LVM Mirroring to obtain a usable backup
From:Brian J. Murrell (bri@interlinx.bc.ca)
Date:Sep 17, 2009 8:34:09 am
List:com.redhat.linux-lvm

On Thu, 2009-09-17 at 11:06 -0400, Stuart D. Gathman wrote:

Using dd from a snapshot does not help the OP.

Right.

He says the dd will take 5-6 hours, and he needs a backup of the system *just before* the upgrade, not hours before.

Which a snapshot will achieve.

The rollback also needs to be quick.

Which a snapshot will achieve.

A snapshot with dd does the "instant" backup part ok, but rollback requires 5-6 hours to copy the snapsnot to a normal LV.

Why would you copy the snapshot anywhere? If you decided you needed a roll-back, you boot from the snapshot of the root filesystem and have the /etc/fstab in that snapshot mount any snapshots of other filesystems he might have made. Personally, I keep separate /, /usr, and /var and so snapshot them all before an upgrade and fix up the /etc/fstab in the snapshot-of-/ to mount the /usr and /var snapshots (rather than the origins).

AFAICT, the only issue the OP has with snapshots is that he fears an upgrade might screw up his LVM configuration. Personally, I think that is a low-probability fear, but everyone has to have their own comfort level I guess.

The OP is correct that creating and breaking a RAID1 mirror does what he needs.

Indeed.

I always build my VGs on md* devices.

I typically have not. I typically don't mirror anything except my backup volume, which fully (as in bare metal restore able) backs up every filesystem I have in my network. For that reason I feel that mirroring the disks in all the machines is overkill.

But granted, building systems on broken mirrors is easy enough and allows one the flexibility of mirroring at a later date if one wants.

In fact I always thought/felt, that given that the MD superblock is at the end of a device (or partition), shrinking the filesystem on a partition and then trying to create an MD mirror with that partition should be doable. Never tried though.

b.