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

Igor Neves igor at 3gnt.net
Mon Mar 29 18:00:15 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.


Apart from any problem you may have in your setup, consider stop using 
3ware controllers and buy areca. 3ware controllers are very, very slow.

You may try to get ride of software raid too, you shouldn't setup drbd 
over OS disks too, you should split everything. I know almost everyone 
want to spend less money possible but setting up data on top of your OS 
disks it's terrible bad ideia!

Good luck.

On 03/28/2010 08:14 PM, Radu Rendec wrote:
> Hello,
> 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).
> TIA,
> Radu Rendec
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Igor Neves<igor.neves at 3gnt.net>
3GNTW - Tecnologias de Informação, Lda

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