[DRBD-user] Re: syncer performance problem

Pavel Semerad semerad at ss1000.ms.mff.cuni.cz
Thu Aug 5 22:49:06 CEST 2004

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

> >
> > if its not that,
> > then try to set the rate to some large figure (100M or something)
> > the syncer in drbd 0.7.0 follows a weird timer based pattern, which I
> > personally dislike, but in our test environments it did work...
> >
> Thanks for the suggestions!
> so I tried upgrading to 0.7.1  as suggested.  But I'm still getting 
> 5MB/s performance...

  I am testing the same version (on 2.4.26 kernel) and have the same problem
(sync speed <5MB/s). After changing from smp (hyperthreading P4) to up kernel,
speed increased (one time it was 20MB/s, but mostly about 15MB/s which is
still slow).
  Disks can do sequential 100MB/s read/write (stripped lvm) and
crossover gigabit ethernet can do 100MB/s with ttcp .
  With tcpdump dumping packets I found that with smp kernel there were
about aprox. 3 second gaps where no packets were on the wire. With up kernel
there are smaller gaps about 1s (it can be normal, I don't know yet :-).

  Sequential writing to device gives 40MB/s, which is relatively good (but
native is 2 times more :-).

  smp kernel (also at 1 processor only) also did deadlock when writing
more data at once (about >80MB with dd or mkreiserfs on 1GB volume).

Pavel Semerad

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