[DRBD-user] Sync slow with drbd 0.7.10 and linux 2.6.11

[Philipp Reisner]

Am Mittwoch, 9. März 2005 23:10 schrieb Harry Edmon:
> I have two 2.6.11 systems with 3ware cards hooked up via drbd 0.7.10.
> When set up freshair2 (8000 3ware card) as the primary and sync it to
> funnel1 (9000 3ware card), it runs 20-30 MBytes/sec.  However, when I
> reverse this (funnel1->freshair2) the sync rate is 7 MBytes/sec.  I have
> tested the network and disk bandwidth by doing a rcp from funnel1to
> freshair2, and I get 27 Mbytes/sec, which seems to eliminates the
> network and the disk.  This is with nothing else running on either
> machine.  All that is left appears to be drbd.
>
> Both units are dual Xeon systems, and have have tried them with both
> hyperthreading on and off.   Anyone have any ideas?  I have attached the
> drbd.conf file.

It seems that the 2.6.11 IO-Scheduling code has some new surprises
ready for DRBD. I need some time to understand this new issues 
completely.

What you can do so far:

  max-buffers 4096
  max-epoch-size 1024

  __AND__
  
  you need to tune the nr_requests parameter of the backing device
  via sys-fs. -> 1024 gave me reasonable performance...

-Philipp
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