[DRBD-user] Full resync vs real-time sync

Gennadiy Nerubayev parakie at gmail.com
Thu Apr 30 23:58:42 CEST 2009

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


On Thu, Apr 30, 2009 at 5:18 PM, Tom Brown <wc-linbit.com@
vmail.baremetal.com> wrote:

>
> I'd expect that if he's seeing sync's running faster than application
> level writes, then there is an issue with write-barriers. DRBD is taking
> steps to provide write-ordering protection, which aren't relevent to
> bulk/block copying of re-syncing.
>
> e.g. http://www.drbd.org/users-guide/re-drbdconf.html
>      no-disk-barrier  ,  no-disk-flushes  ,  no-disk-drain


I've generally established that for best performance on my hardware, I need
no-disk-flushes, no-md-flushes, and no-disk-barrier, and they've all been in
place already. no-disk-drain does not improve anything, and was mentioned by
Lars as a bad idea if the other three are present.

The connection is capable of at least ~900MB/s (Infiniband), and the top
observed DRBD sync speed is 400MB/s as mentioned. For testing purposes, the
metadata is on a ramdisk.

Thanks,

-Gennadiy
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