Hi jf…
>> Mostly curious, don't have experience in such environments, but ... Is
>> this
AFM over NFS or NSD protocol? Might be interesting to try the other option
-- and also check how nsdperf performs over such distance/latency.
As it turns out, it seems, very few people do.
I will test nsdperf over it and see how it performs. And yes, it is AFM → AFM.
No NFS involved here!
-jc
------------------------------
Message: 2
Date: Wed, 9 Nov 2016 17:39:05 +0000
From: Jake Carroll <[email protected]>
To: "[email protected]"
<[email protected]>
Subject: [gpfsug-discuss] Tuning AFM for high throughput/high IO over
_really_ long distances
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
Hi.
I?ve got an GPFS to GPFS AFM cache/home (IW) relationship set up over a
really long distance. About 180ms of latency between the two clusters and
around 13,000km of optical path. Fortunately for me, I?ve actually got near
theoretical maximum IO over the NIC?s between the clusters and I?m iPerf?ing at
around 8.90 to 9.2Gbit/sec over a 10GbE circuit. All MTU9000 all the way
through.
Anyway ? I?m finding my AFM traffic to be dragging its feet and I don?t
really understand why that might be. I?ve verified the links and transports
ability as I said above with iPerf, and CERN?s FDT to near 10Gbit/sec.
I also verified the clusters on both sides in terms of disk IO and they
both seem easily capable in IOZone and IOR tests of multiple GB/sec of
throughput.
So ? my questions:
1. Are there very specific tunings AFM needs for high latency/long
distance IO?
2. Are there very specific NIC/TCP-stack tunings (beyond the type of
thing we already have in place) that benefits AFM over really long distances
and high latency?
3. We are seeing on the ?cache? side really lazy/sticky ?ls ?als? in
the home mount. It sometimes takes 20 to 30 seconds before the command line
will report back with a long listing of files. Any ideas why it?d take that
long to get a response from ?home?.
We?ve got our TCP stack setup fairly aggressively, on all hosts that
participate in these two clusters.
ethtool -C enp2s0f0 adaptive-rx off
ifconfig enp2s0f0 txqueuelen 10000
sysctl -w net.core.rmem_max=536870912
sysctl -w net.core.wmem_max=536870912
sysctl -w net.ipv4.tcp_rmem="4096 87380 268435456"
sysctl -w net.ipv4.tcp_wmem="4096 65536 268435456"
sysctl -w net.core.netdev_max_backlog=250000
sysctl -w net.ipv4.tcp_congestion_control=htcp
sysctl -w net.ipv4.tcp_mtu_probing=1
I modified a couple of small things on the AFM ?cache? side to see if it?d
make a difference such as:
mmchconfig afmNumWriteThreads=4
mmchconfig afmNumReadThreads=4
But no difference so far.
Thoughts would be appreciated. I?ve done this before over much shorter
distances (30Km) and I?ve flattened a 10GbE wire without really
tuning?anything. Are my large in-flight-packets
numbers/long-time-to-acknowledgement semantics going to hurt here? I really
thought AFM might be well designed for exactly this kind of work at long
distance *and* high throughput ? so I must be missing something!
-jc
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Message: 3
Date: Wed, 09 Nov 2016 18:05:21 +0000
From: Jan-Frode Myklebust <[email protected]>
To: "[email protected]"
<[email protected]>
Subject: Re: [gpfsug-discuss] Tuning AFM for high throughput/high IO
over _really_ long distances
Message-ID:
<CAHwPathy=4z=jDXN5qa3ys+Z-_7n=tsjh7cz3zkzfwqmg34...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Mostly curious, don't have experience in such environments, but ... Is this
AFM over NFS or NSD protocol? Might be interesting to try the other option
-- and also check how nsdperf performs over such distance/latency.
-jf
ons. 9. nov. 2016 kl. 18.39 skrev Jake Carroll <[email protected]>:
> Hi.
>
>
>
> I?ve got an GPFS to GPFS AFM cache/home (IW) relationship set up over a
> really long distance. About 180ms of latency between the two clusters and
> around 13,000km of optical path. Fortunately for me, I?ve actually got
near
> theoretical maximum IO over the NIC?s between the clusters and I?m
> iPerf?ing at around 8.90 to 9.2Gbit/sec over a 10GbE circuit. All MTU9000
> all the way through.
>
>
>
> Anyway ? I?m finding my AFM traffic to be dragging its feet and I don?t
> really understand why that might be. I?ve verified the links and
transports
> ability as I said above with iPerf, and CERN?s FDT to near 10Gbit/sec.
>
>
>
> I also verified the clusters on both sides in terms of disk IO and they
> both seem easily capable in IOZone and IOR tests of multiple GB/sec of
> throughput.
>
>
>
> So ? my questions:
>
>
>
> 1. Are there very specific tunings AFM needs for high latency/long
> distance IO?
>
> 2. Are there very specific NIC/TCP-stack tunings (beyond the type
> of thing we already have in place) that benefits AFM over really long
> distances and high latency?
>
> 3. We are seeing on the ?cache? side really lazy/sticky ?ls ?als?
> in the home mount. It sometimes takes 20 to 30 seconds before the command
> line will report back with a long listing of files. Any ideas why it?d
take
> that long to get a response from ?home?.
>
>
>
> We?ve got our TCP stack setup fairly aggressively, on all hosts that
> participate in these two clusters.
>
>
>
> ethtool -C enp2s0f0 adaptive-rx off
>
> ifconfig enp2s0f0 txqueuelen 10000
>
> sysctl -w net.core.rmem_max=536870912
>
> sysctl -w net.core.wmem_max=536870912
>
> sysctl -w net.ipv4.tcp_rmem="4096 87380 268435456"
>
> sysctl -w net.ipv4.tcp_wmem="4096 65536 268435456"
>
> sysctl -w net.core.netdev_max_backlog=250000
>
> sysctl -w net.ipv4.tcp_congestion_control=htcp
>
> sysctl -w net.ipv4.tcp_mtu_probing=1
>
>
>
> I modified a couple of small things on the AFM ?cache? side to see if it?d
> make a difference such as:
>
>
>
> mmchconfig afmNumWriteThreads=4
>
> mmchconfig afmNumReadThreads=4
>
>
>
> But no difference so far.
>
>
>
> Thoughts would be appreciated. I?ve done this before over much shorter
> distances (30Km) and I?ve flattened a 10GbE wire without really
> tuning?anything. Are my large in-flight-packets
> numbers/long-time-to-acknowledgement semantics going to hurt here? I
really
> thought AFM might be well designed for exactly this kind of work at long
> distance **and** high throughput ? so I must be missing something!
>
>
>
> -jc
>
>
>
>
>
>
> _______________________________________________
> gpfsug-discuss mailing list
> gpfsug-discuss at spectrumscale.org
> http://gpfsug.org/mailman/listinfo/gpfsug-discuss
>
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