[DRBD-user] drbd slow sync and 3ware controller

Radu Rendec radu.rendec at mindbit.ro
Sun Mar 28 21:14:19 CEST 2010

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


I have 2 (storage) servers running drbd on top of LVM logical volumes.
Server 1 has hw raid 5 with 3ware 9650 controller and server 2 has raid
5 sw raid. I'm using protocol C, syncer rate 50M.

The only problem is sychronizing from server 2 to server 1 (actually
writing to the 3ware card) - I only get 5-6 M / s, with all CPUs on
server 1 in ~100% iowait.

And now the really strange thing: this only happens during sync. Once
the sync is complete, I can successfully write at ~ 50M/s on server 2
drbd device, with almost no load on server 1.

Syncing from server 1 to server 2 (writing to the sw raid) works as
expected: ~ 50M / s, no load on either servers.

The issue seems to be related to the combination between the 3ware card
and the drbd (initial) sync. But I'm totally clueless, since I can't
figure out what's the difference between the initial sync and writing
data when it's already synchronized.

I'm kindly asking for any suggestions. If you reply, please cc my
address (I'm not subscribed to the list).


Radu Rendec

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