Re: [Xen-users] How (not) to destroy a PostgreSQL db in domU on powerfail

[Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>]

On Mittwoch 04 März 2009 Michael Monnerie wrote:
> On Mittwoch 04 März 2009 Fajar A. Nugraha wrote:
> > Is your domU filesystem (/path/root20090113.xvd ?) located on top
> > of LVM? If yes, then AFAIK LVM does not honor write-barriers.
>
> Indeed. LVM is bad? I've read LVM is suggested in order to have an
> easier backup with snapshots. But if the result is that your XEN domU
> gets destroyed on a power outage - damn LVM.
>
> Can someone confirm that LVM does not honor write-barriers?

http://lkml.org/lkml/2008/5/16/390
http://hightechsorcery.com/2008/06/linux-write-barriers-write-caching-
lvm-and-filesystems

If I understand correctly, turning off disk cache write cache should be 
enough to be save, even when using LVM. Is it really XEN that messed the 
disk, or something else? Could the Areca controller driver do something 
wrong? I'd really love to get a stable and data-secure system, as you 
might understand.

mfg zmi
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