[linux-lvm] Powerfailure and snapshot consistency

[Phillip Susi]

On 3/28/2011 1:24 PM, Stuart D. Gathman wrote:
> Ah, thank you!  Yes, I am using ext3 with EL5.5 defaults, and will now
> learn
> about the barrier option.  Seems like a good thing to turn on when "replace
> battery" comes up on the ups.
> 
> It sounds like dumb luck/divine mercy that the raid 1 PV on which the
> production LV resides did not have a similar issue.

It actually should be on all the time, which is why it defaults to on in
ext4.  A UPS doesn't help if the kernel crashes or some hardware fails.
 I have no idea why incidents like this are not common place with ext3
since it is inherently unsafe without barriers, whether you are using
lvm or mdadm or not.