Mailinglist Archive: opensuse-ha (30 mails)

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Re: [opensuse-ha] ext4 failure on cluster
On Fri, 2014-08-15 at 07:57 -0400, Ron Kerry wrote:
On 8/15/14, 7:45 AM, Lars Marowsky-Bree wrote:
With ocfs2, it's fine. It still works though, even if we disable one
of the nodes. We have only old hardware so it would be pointless
having ext4 nodes with only one active at a time: we may as well go
back to our single file server.
I'm not sure this holds. There's a penalty needed for syncing and
locking. Have you benchmarked if a single node is really slower than
two? Especially a write-heavy workload probably won't, and it'll go very
much downhill if you have metadata-intensive jobs (e.g.,
creating/deleting/stating lots of files/directories).

The main reason for HA is, well, availability, not performance, thus
going back to a single server is likely worse than this anyway.

True enough, but the performance of an active-active HA configuration with
two or more nodes serving
NFS or CIFS can be well in excess of what a single server is capable of
doing. This all depends on
the underlying disk hardware. Many time that hardware may be capable of far
more bandwidth than a
single server can drive by itself. In this active-active clustered
environment the performance
achievable by any single node will be less than what it can do on its own,
but the combined
performance of many nodes to the same shared-clustered disk will be able to
reach the bandwidth
capability of the underlying disk hardware.

If a single node can drive your disk hardware at peak bandwidth, than as Lars
says you will get no
performance benefit (in fact you get a performance degradation) from an
active-active HA
configuration ... just the availability benefit.

Hi. It's the availability which is more important here. We're never
going to get performance anyway as we can't afford new hardware.

--

Ron Kerry rkerry@xxxxxxx
Global Product Support - SGI Federal



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