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Re: [Gluster-devel] Performance Translators' Stability and Usefulness

From: Gordan Bobic
Subject: Re: [Gluster-devel] Performance Translators' Stability and Usefulness
Date: Sat, 04 Jul 2009 11:52:03 +0100
User-agent: Thunderbird (X11/20090625)

Shehjar Tikoo wrote:
We can definitely vouch for a higher degree of stability of the
releases. Otherwise, I dont think there is any performance translator we
can call completely stable/mature because of the roadmap we have for
constantly upgrading algorithms, functionality, etc.

I'm only talking about release versions - while there are still consistently trippable bugs in my use case(s) (e.g. that consistent failure with immediate access after mounting the AFR volume) I'm not going to venture into the git head. :)

Any particular suggestions on which performance translator combination would be good to apply for a shared root AFR over a WAN? I already have read-subvolume set to the local mirror, but any improvement is welcome when latencies soar to 100ms and b/w gets hammered down to 1-2.5 Mb/s.

WANs are generally characterised as having a large bandwidth-delay
product. That basically means, for good throughput, we should be
pipelining as much data as possible over the link, so that the long
latency overhead can be mitigated or amortised by sending larger amount
of data for the same fixed overhead.

That said, what particular workload is it that gives you a throughput of
1-2.5 Mb/s?

That's the WAN bandwidth, so it's a theoretical maximum, not the observed throughput.

When you say "latencies soar to 100ms", does that mean, these are just
unusual spikes or is that the normal latency observed?

I was talking about ping time. I've actually checked it and its more like 30ms (on an idle connection), but that's still 4x more than disk access time and 300x more than LAN ping time.

It'd help to see your volfiles and how the performance translators are

I'm not using the performance translators at the moment, It's only with 2.0.2 that I've found it stable enough for my use case without any translators. But since you've mentioned it, how should the performance translators be arranged/nested?


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