[DRBD-user] replication link stability

Digimer linux at alteeve.com
Thu Feb 16 16:43:27 CET 2012

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

On 02/16/2012 09:18 AM, Piotr Kandziora wrote:
> Hi,
> I have two servers with dedicated replication link (WiFI - 48Mbit/s). My
> clients are connecting via other network link (100Mbit/s) to SAMBA service.
> When they are copying files then replication link is very unstable - I
> can see a lot of NetworkFailure statuses. Finally, they are disconnected
> from SAMBA share (what is strange).
> I think that dedicated network link is ok, because when I manually copy
> files between two samba locations then copying is fine.
> What is the reason of this behaviour? Any solution?
> Below you can find my net and syncer section from drbd.conf:
>      net {
>                 max-buffers 2048;
>                 max-epoch-size 2048;
>                 unplug-watermark 128;
>                 sndbuf-size 0;
>         }
>          syncer {
>                 c-min-rate 10M;
>                 rate 10M;
>                 al-extents 127;
>         }
> Best regards
> Piotr Kandziora

Hi Piotr,

  Samba (and similar protocols) are generally pretty forgiving of
network issues, so it's not a surprise that they work where DRBD does
not. DRBD is designed for high speed/low latency environments, and has a
fair bit of attention paid to fault detection and recovery. If it sees a
network fault, even a short one, it has to assume the link has failed
and recovery is needed. This does not lend itself well to use on
slow/error prone networks.

  Is it possible to use a wired connection for the DRBD replication? If
not, I would suggest looking at DRBD Proxy instead, as it is designed to
run over slow/unstable links, but it is asynchronous, so be advised that
consistency is not always guaranteed.

E-Mail:              digimer at alteeve.com
Papers and Projects: https://alteeve.com

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