On 2019-06-29 7:26 a.m., Marcus Schopen wrote:
Hi,
i am looking for a solution to keep qcow2 images of two KVM hosts sync.
(about 20 guests, images size max 100 GB). Unfortunately, shared
storage is not available to me. My first look was on Gluster, but after
what I've read so far, there might be performance issues here. I don't
need real HA. If the first host fails, it would be sufficient for me to
manually start the KVM guests on the second host. Ultimately, I just
want to avoid having to restore the images from the nightly backup and
have a maximum "data loss" of 24 hours. Is drdb a alternative here? And
what should I pay particular attention to when setting up, split brain
etc.?
Cheers
Marcus
Hi Marcus,
I use GlusterFS for VM image storage. Most of them are RAW files
and QCOW2 is fine too. There are things to watch for performance. In a
setup we have for a client, the Windows File server (8TB + 5TB) is now
screaming compared to the old setup: 120 MBps! And the overtaxed mail
server (CentOS 7 Linux VM running CommuniGate) on the same cluster is
doing fine too (low IOwait considering the 1TB+ Public Folders, 140
Outlook users and a total of 2.5 TB of emails).
This setup is configured in three way replication. The 3 servers
are Supermicro using LSI RAID 6 arrays. GlusterFS bricks are ontop thin
provisioned LVM logical volumes. Watch out for lvm / filesystem optimal
alignment VS your physical RAID arrays.
Just keep in mind that with 2 servers, you are exposed to split
brain issues. The other way of doing it in the above setup would be 2+1
replication with an arbiter: It would saves space and still enforce
quorum. But many things i read are pointing to 3 way replication for
simplicity and stability.
Here are the infos about this Gluster cluster:
3 x Supermicro 3U servers with each:
1 x Xeon E5-2609 CPU
32 Gig RAM
Integrated LSI SAS 2208
32 TB Array consisting of 8 x HGST NAS 7200 RPMs drives in RAID 6
2 x Integrated Intel X540-AT2 10 Gbps ethernet
We are considering of adding SSD caching, still looking for the best way
of doing it... (LVM Cache / Gluster Tiering / etc)
There are 2 KVM Servers running VMs with dual E5-2630v2 CPU, 96 Gigs RAM
and dual 10 Gbps ether
The next part will be to add OVirt.
Be sure to simulate what you want to achieve before going in prod. Test
disconnection of a node, etc. I like Gluster but there are situations
that you must know what you're doing. I paid a premium for the Red Hat
Gluster Video self training and it is not a good course IMHO (more of an
intro...), i didn't learn what was of interest to me (highly technical)
and i taught i could ask questions: They direct you to tech support and
you must have a contract.... They seem to want to direct you to their
"design" team.
I didn't find any "best practices", not real good guidelines and
explanations...
A real important thing to consider: The network part. Look for bonding
+ dual attach switch and for ECM Routing + OSPF on the servers /
network. I'm still searching for the best network setup to get
performance and full redundancy.
Hope this helps.
Guy
--
Guy Boisvert, ing.
IngTegration inc.
http://www.ingtegration.com
https://www.linkedin.com/pub/guy-boisvert/7/48/899/fr
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