[DRBD-user] Slow initial full sync

Lutz Vieweg lvml at 5t9.de
Wed Oct 29 11:33:46 CET 2014

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

On 10/29/2014 05:34 AM, aurelien panizza wrote:
> I've got two servers connected via a switch with a dedicated 1Gb NIC. We have a SSD raid 1 on both
> servers (software RAID on Redhat 6.5).

> Full sync between the primary and the secondary is from 3MB/s to 12MB/s

> iostat report 100%util on /dev/drbd0 on the secondary.

Check whether there's a block device with a low max_hw_sectors_kb value
in your device stack:

> ls -1 /sys/block/*/queue/max_hw_sectors_kb | xargs -i bash -c 'echo -n "{} " ; cat {}'

If you see small values for max_hw_sectors_kb in one of these, chances
are that just inefficient smalls blocks are transferred - you can
also find a discussion on this in the DRBD mailing list archive, just
search for max_hw_sectors_kb.


Lutz Vieweg

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