[DRBD-user] DRBD terrible sync performance on 10GigE

Philipp Marek philipp.marek at linbit.com
Thu Dec 3 08:47:48 CET 2015

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

> However, no matter the way I configure DRBD, the throughput is limited
> to 100MB/s. It really looks like some hardcoded limit. I can reliably
> lower performance by tweaking the settings, but it never goes over
> 1Gbit (122MB/s are reached for a couple of seconds at a time). I'm
> really pulling my hair on this one.
> Output from cat /proc/drbd on slave :
> version: 8.4.5 (api:1/proto:86-101)
> srcversion: EDE19BAA3D4D4A0BEFD8CDE 
>  0: cs:SyncTarget ro:Secondary/Secondary ds:Inconsistent/UpToDate C
> r----- ns:0 nr:4462592 dw:4462592 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
> ep:1 wo:f oos:16489499884 [>....................] sync'ed:  0.1%
> (16103024/16107384)M finish: 49:20:03 speed: 92,828 (92,968) want:
> 102,400 K/sec
This is not throughput, but the initial synchronisation, as you note:

> Apparently initial synchronisation is supposed to be somewhat slow, but
> Not this slow... Furthermore it doesn't really react to any attempt to
> Throttle sync rate like 
> Drbdadm disk-options --resync-rate=800M all
You're running on 8.4 - the "resync-rate" doesn't apply any more.


and the Users' Guide, especially 15.3:

Furthermore, 8.4.6 has already been released ...

[ and if you want/need Pacemaker for newer Debian - LINBIT has them. ]

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