Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Tue, May 05, 2009 at 03:57:16PM -0400, Gennadiy Nerubayev wrote:
> On Sat, May 2, 2009 at 2:06 PM, Lars Ellenberg <lars.ellenberg at linbit.com>wrote:
>
> > nice. you are going into page cache here, mostly
> > (how much RAM did you say you have?)
> >
>
> 4GB on one node, 8GB on the other. I verified that benchmark numbers are the
> same on both nodes.
>
> > dd if=/dev/zero of=/dev/drbd0 bs=4M count=1000 oflag=direct
> > > 4194304000 bytes (4.2 GB) copied, 17.6633 seconds, 237 MB/s
> >
> > do variations.
> > use 512k, 1M, 2M, 100M.
> >
>
> After rerunning these various sizes, there is no appreciable performance
> difference from bs=4M, in either connected or disconnected mode, across all
> flags. I didn't do connected benchmarks on a single core, as the resync
> performance dropped by 100MB/s with only one core..
Ah. right.
in that case, try "syncer { cpu-mask 3; }" and see if that improves
performance during normal operation on your dual core cpu.
>
> repeat measurements.
> > see how reproducable they are.
>
>
> Very consistent, with a margin of error of a few megabytes one way or the
> other; no significant fluctuations.
>
> also read up about the "al-extents" drbd.conf parameter, "max-buffers",
> > and the rest of the usual tuning stuff. the activity log updates will
> > slow you down on streaming writes.
>
>
> Neither has any noticeable effect (buffered and fsync may actually be a
> little slower with larger max-buffers), but I am running with the metadata
> on a ramdisk..
>
> what is your rtt, small packets, large packets?
> > ping -w 5 -f -s 64 other-node
> > ping -w 5 -f -s 5000 other-node
>
>
> PING 10.0.0.3 (10.0.0.3) 64(92) bytes of data.
> .
> --- 10.0.0.3 ping statistics ---
> 147010 packets transmitted, 147010 received, 0% packet loss, time 5001ms
> rtt min/avg/max/mdev = 0.020/0.023/0.153/0.003 ms, ipg/ewma 0.034/0.023 ms
>
> PING 10.0.0.3 (10.0.0.3) 5000(5028) bytes of data.
>
> --- 10.0.0.3 ping statistics ---
> 70976 packets transmitted, 70976 received, 0% packet loss, time 5001ms
> rtt min/avg/max/mdev = 0.043/0.047/0.164/0.009 ms, ipg/ewma 0.070/0.049 ms
>
> Hope that helps,
>
> -Gennadiy
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--
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com
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