Saso Kiselkov wrote:
On 7/23/14, 2:18 PM, Miles Fidelman via illumos-discuss wrote:
Saso Kiselkov via illumos-discuss wrote:
On 7/23/14, 1:38 PM, Miles Fidelman via illumos-discuss wrote:
Saso Kiselkov wrote:
On 7/23/14, 12:57 PM, Miles Fidelman via illumos-discuss wrote:
Hi Folks,
Is there anything like DRBD or HAST for illumos? Seems like ZFS +
DRBD
would be really sweet for high availability clusters - but so far,
none
of the pieces are together in one place.
Trying to get to a small cluster w/ Xen+ZFS+HA
ZFS: illumos, FreeBSD, not really stable anywhere else
Replication: DRBD for Linux, HAST for BSD*, ??? for illumos
Xen: Linux, NetBSD
Sigh...
AFAIK there's no native remote block-level synchronous replication
solution for Illumos.
For async replication, incremental snapshots are the way to go. Just
transfer an incremental snapshot every 30-60s. They're relatively
inexpensive and robust, so pool corruption doesn't immediately get
propagated to the replication pair.
For sync replication I personally use SAS fabrics and mirrored pools
(conceptually, this is essentially what sync replication does, only
over
a special protocol). Passive SAS cabling can run 3m (so rack-to-rack is
possible) and 20m with active cabling (room-to-room even). If longer
links are needed I'd opt for iSCSI. At Nexenta we've got some early
stuff in ZFS that allows us to prioritize reads & writes to mirror
sides, but it's still pretty new and not battle proven.
I know these are conceptually not exactly the same as DRBD or HAST, but
functionally it's identical.
Thanks for the model. It's kind of overkill for what we're doing - tiny
(4-node) cluster, mostly for development, but we run mail and a list
manager in a HA-configuration.
The basic stack, right now is:
VM (Debian Dom1)
DRBD
LVM
software raid
Xen (Debian Linux Dom0)
Pretty stable, except... if you're following the Linux world, and the
stuff w/ systemd (moving lots of core functions into a monolithic blob)
- instead of upgrading Linux, I've been seriously looking at migrating
to either a BSD or Solaris based stack. Complicated by having a couple
of older machines in our cluster that don't have hardware virtualization
extensions.
Kind of what I'd LIKE to do is:
VM (illumos if I can get all the mail, list, antivirus, etc. to run,
otherwise Linux)
<something like DRBD or HAST>
ZFS (exported ZVOL)
Xen (illumos-based Dom0)
Can't seem to find a full set of comparable software in either the BSD*
or illumos worlds. Sigh...
For the VM stuff, I'd recommend having a look at SmartOS. Sure, you
won't be able to do KVM on machines without HVM and EPT support, but
you'll still be able to run zones on there and run your mail (latest
postfix, postgrey, etc.), AV (latest clamav), web (latest apache, nginx,
ruby, php, etc.), DB (latest mysql, postgres, etc.) and other stuff. All
of these are available in packaged form from the Joyent repos, so no
need to compile from source. And to insure disaster recovery, unless you
need sync replication (and judging by your description of your
environment as "tiny"), run an incremental zfs send/recv job and be done
with it - if need be, you can even run it every 10s.
SmartOS looks really sweet.
I'm just quite sure I'm ready to give up:
Xen - I rely prefer it's overall architecture and environment to any of
the other virtualization solutions
synchronous replication
The combination makes failover a no-brainer. With zfs send/receive,
somethings going to get out of whack, sooner or later - good for
backups, not so good for HA failover.
If you think sync replication absolves you of the need to do regular
backups, you are so in for a bad a surprise down the road.
We do that too! But backups are for disaster (and stupidity) recovery,
not automatic failover.
--
In theory, there is no difference between theory and practice.
In practice, there is. .... Yogi Berra
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