Cool! DRBD over ZVOLs looks like it could be a really sweet, and
easier-to-manage HA environment.
Thanks for the advise!
Miles
Simon Ironside wrote:
Hi Miles,
Yes - I run DRBD inside KVM virtual machines in production just fine.
There were no performance issues or real gotchas that I've encountered.
I was just careful to not base the VM's storage on DRBD *outside* the
VM in case I accidentally had both VMs running on the same physical
server ;) I was also careful to maintain separate front and back
networks by bridging two separate virtual NICs in the VM to two
separate physical NICs on two separate networks on the physical host
just as I do with DRBD on "real" servers.
HTH,
Simon.
On 23/07/14 23:23, Miles Fidelman wrote:
Hi Folks,
I'm wondering if something is doable - comments please:
I have a very specific situation where I'm trying to maintain a legacy
high-availability application running in a Xen VM (Linux DomU).
Current stack (per node, in a 2-node HA cluster):
Applications
VM (Linux DomU) --- auto failover to node 2 ----
DRBD ---- replicated to node 2 ----
LVM
md raid
Xen (Linux Dom0)
We're looking at migrating our infrastructure to an OpenSolaris base
(probably SmartOS), which will end up looking like this:
VM (Linux KVM or Zone) ------------auto failover ot node 2 -----
<synchronous replication> ----- to node 2 ----
ZFS (exporting a ZVOL)
KVM (or Zones)
SmartOS
The kicker, is that there is no available equivalent to DRBD for the
illumos ecosystem - hence, my thought is to mount the ZVOL block device
inside the 2 virtual machines, and use DRBD running on Linux inside the
pair of VMs to achieve storage replication.
Will DRBD run inside a virtual machine? Will it give any kind of
reasonable performance? Are there any serious gotchas to watch out for?
Three notes re. motivation and thinking:
- for all our other applications, we're doing application layer
replication (e.g., database sync) - but for smtp and list processing
this doesn't seem easily doable (too many queues and messages in flight,
asynchronously)
- looking to move from Linux for a number of reasons, but
particularly ZFS
- looked at BSD, which has HAST as an equivalent of - virtualization is
a mixed bag (Xen on NetBSD, but not FreeBSD; KVM sort of, a new
hypervisor for FreeBSD), and ZFS is only stable on FreeBSD - can do some
things on FreeBSD, some on NetBSD, but not all on the same one - and
right now the illumos world seems to be gaining lot of momentum as the
alternative open-source Unix
Thanks very much,
Miles Fidelman
--
In theory, there is no difference between theory and practice.
In practice, there is. .... Yogi Berra
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