[DRBD-user] DRBD write after write (cache)

J. Ryan Earl oss at jryanearl.us
Wed Feb 9 19:51:24 CET 2011

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


On Sat, Feb 5, 2011 at 4:45 AM, ionral <daniele.nuzzo at email.it> wrote:

> if I check the status of drbd the following response is:
>
>  0: cs: Connected ro: Primary / Primary ds: UpToDate / UpToDate C r ----
>    ns: 640864680 nr: 135234784 dw: 776099464 dr: 1520599328 al: 836478 bm:
> 2185 lo: 0 pe: 0 ua: 0 ap: 0 ep: 1 wo: b OOS: 0
>
> I do not know if it is positive that the method is to write after is
> Barrier
> .... reading the manuals of drbd I noticed that in these cases (BBU)
> performance would be better for a wo:n
>
> What do you think?
>

Modify your drbd.conf to look more like:

  disk {
    on-io-error   detach;
    # It is good to have backed up write caches
    no-disk-barrier;
    no-disk-flushes;
    no-disk-drain;
    no-md-flushes;
    use-bmbv;
  }

This will completely turn off write ordering which.  I have measured
performance gains doing this with backed-up write caches.

-JR
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