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xen-users
Re: [Xen-users] How (not) to destroy a PostgreSQL db in domU on powerfa
On 03/04/2009 08:28 PM, Javier Guerra wrote:
On Wed, Mar 4, 2009 at 11:35 AM, Michael Monnerie
<michael.monnerie@xxxxxxxxxxxxxxxxxxx> wrote:
I wonder why there's no documentation about this problem. There are
people using XEN in production machines - are they not scared by the
actual behaviour? Even if I have UPSes and whatever, a crash can always
occur. I have a customer who wants to use XEN to replace 10 small
servers by a single one, but currently I'm reluctant to recommend XEN
because I worry about the data. Imagine you have 10 servers not coming
up after a problem - it could take hours to get every single server up
and running again.
it certainly warrants more investigation. but i guess very few
production machines are using imagefiles on top of XFS. the common
scenarios are either block devices or imagefiles on top of
OCFS/NFS/ext3
But are we sure that it cames from XFS ?
Mike seems to describe that he has everything OK with the requirement of
XFS. so as I said previously either XFS is doing nasty things when it's
in XEN or it is LVM that is doing nasty things in XEN or LVM+XFS ...
BTW his first hypothesis was that XEN was lying about fsync, which I
guess is not that simple but is at the end something approching.
In fact it could be quite interesting (but a bit time consuming) to have
a normal linux installation with XFS and postgresql and stress it a
little bit (otherwise I guess that you won't face the problem) and
meanwhile unplug it.
And do the same with XFS + LVM.
And one more test with XEN+XFS in domU+postgresql in domU.
I insists on the fact that the postgresql should be stressed otherwise
data won't be much modified and no nearly no chance of corruption.
Matthieu.
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