[stgt] Quick Failover & Scalability questions
fujita.tomonori at lab.ntt.co.jp
Thu Oct 14 11:42:00 CEST 2010
On Wed, 13 Oct 2010 10:26:25 -0600
"Mark Lehrer" <mark at knm.org> wrote:
> I have a few tgtd servers running and they are doing very well. I would
> like to add a 2nd server as a backup so I have one question. Assuming that
> the block device mirroring and IP/Mac failover are perfect ( kind of like
> assuming a frictionless surface in physics :) ), how well does stgt fail
> over to a 2nd server?
I think that there are people that use such configuration.
> The simplest would be for the clients to reconnect to the new server and
> re-establish communications. However, how painful would it be for the new
> server to keep the same sockets open for a truly seamless failover? Again,
I don't think it matters. The simplest solution (multipath) works well
for lots of people. Sharing the state between two hosts is too
> I am only concerned about the tgtd internal states at this point - assume
> that the block device mirroring as well as the
> keepalived/heartbeat/iptables/fencing/etc issues are handled already (though
> there would obviously be a good bit of integration work there!).
> My 2nd question - I am starting to play with things like ionice and
> scalability. One critical aspect of scalability is limiting the first
> connection's performance so it doesn't degrade so quickly as more clients
> come online. It appears that ionice will probably not have the features I
> need; is this on the tgtd roadmap? Even something as basic as a generic "io
> operations per second" would be a good start.
We've just aded the feature to get such stats.
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