[DRBD-user] drbd-0.7.0 with linux-2.4. slow?

Bernd Schubert bernd-schubert at web.de
Sun Aug 1 22:38:44 CEST 2004

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Hello Lars and all,

> well...
> if it does, its a serious bug.
> it did not happen to me so far.

switching the protocols worked fine :)

By switching to protocol B we did not gain a noticeable performance increase, 
but after switching to protol A 
"iozone -s 1g -r 1m  -o -i 0" (not via nfs but directly on the server) now 
shows 16-18MB/s, instead of the previous 10-12MB/s. More important for us are 
the nfs-client numbers (measured with 'time cp /local_disk/... /home/...', 
which will happen in practice very often on our systems):

1 client: 9 - 10 MB/s
2 clients: 7.5 - 8 MB/s
4 clients: 4 - 4.5 MB/s

(/home exported with the sync option)

Thats still not what we got with 2.6.7 (4x7.5MB/s) but still much better than 
what we get with protocol C and 2.4.27-rcX.

With protocol C we also had very high latency numbers, which e.g. slowed down 
compiling of projects dramatically. With protocol A this problem is also gone 
away :)

> what you can do to try and tune drbd:
> play with sndbuf-size
>      increasing it may help throughput,
>      decreasing it may help latency,
>      ... or vice versa ... it depends ...
> play with the mtu of the link (jumbo frames)
> play with max-buffers

Well, I played with all of it (max-buffers,  max-epoch-size, sndbuf-size) but 
it didn't help/change so much.

The current values are:

                sndbuf-size 524288;
                max-buffers 16384;


PS: Lars, do you want me to redo the latency tests, now with protocol A?

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