[ClusterLabs] Antw: SAN, pacemaker, KVM: live-migration with ext3 ?

[Ulrich Windl]

>>> "Lentes, Bernd" <bernd.lentes at helmholtz-muenchen.de> schrieb am 05.09.2018
um
18:13 in Nachricht
<2073407402.9976609.1536164024840.JavaMail.zimbra at helmholtz-muenchen.de>:
> Hi guys,
> 
> just to be sure. I thought (maybe i'm wrong) that having a VM on a shared 
> storage (FC SAN), e.g. in a raw file on an ext3 fs on that SAN allows 
> live-migration because pacemaker takes care that the ext3 fs is at any time

> only mounted on one node. I tried it, but "live"-migration wasn't possible.

> The vm was always shutdown before migration. Or do i need OCFS2 ?
> Could anyone clarifies this ?

Hi Bernd,

following you attempts to run VMs in a cluster always made me wonder why you
ignore advice from people who have a working configuration.
What you seem to do is have an ext3 filesystem that hosts image files for the
VM, and you mount that filesystem on multiple nodes at once I guess. From the
VM and image perspective that may work, but not from the ext3 filesystem
perspective: It's very likely that your filesystem gets corrupted beyond being
able to repair (Read: complete data loss possible).
If you do not mount the ext3 filesystem on multiple nodes, you cannot
live-migrate a VM with Xen (and probably also with KVM). AFAIK the same VM
image must be present on both nodes taking part of a live migration. You could
put the images on raw disks (one image per disk) or use a LVM LV, or use files
on a cluster filesystem. The latter may have performance issues, especialy the
cLVM/OCFS combination...

Regards,
Ulrich

> 
> 
> Bernd
> 
> -- 
> 
> Bernd Lentes 
> Systemadministration 
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