Hi Philippe,
On 24/01/14 10:23, Philippe Schwarz wrote:
Hi Philippe,
Maybe you have thought about this, but does it make sense for your
use case to have a PVE-HA cluster, that is dependent on a third
storage non-HA server?
Do you REALLY need the HA capacity?
I think that the 10 Gbit network connection will help most
connecting PVE servers with storage backend, be it another PVE
server or a storage one.
Hi,
thanks for your (clever) answer.
I thought i could use the (one of the amazing) features of ZFS (like
zfs send zfs receive) to avoid buying a costly second storage server.
Costly because of the amount of disks.
So having a 2nodes cluster with a master/slave storage SAN, was my idea.
But, you're right: A HA cluster for pve, with a non-HA storage is a
non-sense.
But, i'm not confident with the idea of virtualizing the ZFS storage,
loosing by the way the rock-solid, direct access to hardware features
and self-healing capabilities of ZFS.
Another question:In case of blade system; is the fencing devicing
still useful ?
Never used a blade system myself, but I think that you need fencing
anyway for a cluster (maybe the blade system provides a fencing system).
Ok, let's assume i don't need the HA and will migrate manually a VM.
I'm in a secondary school and can afford a few minutes (maybe hours if
it occurs once a year maximum ..) downtime.
What does it change to my infrastructure questions ?
Proxmox allows you to migrate disk from one storage to another with the
VM up. You will notice slow-down in disk access, of course; but no
downtime. Also you can migrate active VMs from one PVE server to another
if using shared disk.
Otherwise, moving a full VM from local disk in a PVE server to another
PVE server, will depend on the size of the disks, disk read and write
performance, and network connection between PVE nodes. Using SATA 7K2
disks and gigabit interconnect, I think that our ~100GB disk VM takes
about 1h-1h30 to migrate from one PVE server to another.
Anyway, I'm not sure you're doing the right questions. Migration of VMs
is an issue, but only if you need to move the VMs between PVE servers
when they are working.
But HA usually is to protect yourself from hardware failure. If you
don't have HA and a PVE server goes down, then you can't migrate the VM;
you may create a new one with his disks, if disks are not in the PVE
server; otherwise you must recover from backup, or fix the failed
server, or put the failed server disks in another server if they are ok.
For me the critical part is the hard disk storage, so you must plan to
have at least 2 hot copies on different servers to be protected from Hw
failure. That will help recovering from failure, even if you have to do
it by hand. I'm sorry to say that having a unique ZFS server won't help
with that! If the server crashes you don't have access to the disks :)
Cheers
Eneko
--
Zuzendari Teknikoa / Director Técnico
Binovo IT Human Project, S.L.
Telf. 943575997
943493611
Astigarraga bidea 2, planta 6 dcha., ofi. 3-2; 20180 Oiartzun (Gipuzkoa)
www.binovo.es
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