[DRBD-user] painfully slow sync

Peter Stamfest peter at stamfest.at
Tue Jan 27 08:05:45 CET 2004

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


On Mon, 26 Jan 2004, Dave Dunkin wrote:

> On Jan 26, 2004, at 4:26 PM, Lars Ellenberg wrote:
> 
> > / 2004-01-26 15:48:14 -0600
> > \ dave at gottathink.com:
> >> Quoting Lars Ellenberg <Lars.Ellenberg at linbit.com>:
> >>
> >>> / 2004-01-25 23:38:08 -0800
> >>> \ Dave Dunkin:
> >>>> I've got drbd set up on two RedHat 9 nodes with 60GB software RAID1
> >>>> devices I'm trying to mirror. I started it up for the first time 
> >>>> and it
> >>>> started with a SyncAll from the primary to the secondary at around
> >>>> 10MB/sec (on a private 100Mbps network). Then at almost exactly 30%
> >>>> though the sync, the sync speed dropped to an abysmal 500KB/sec. 
> >>>> I've
> >>>> tried upping the minimum and setting the nice level, but nothing 
> >>>> seems
> >>>> to improve the situation. I tried stopping and restarting the sync
> >>>> process and the same thing happened at 30%.


I am repeating myself (have a look at the list archive, it might even be a
FAQ): I have seen this with cheap NICs. Switched to 3com cards and
everything went fine afterwards. This was a long time ago (0.6.1_pre
something). I do not know if this problem has ever been identified and
solved and I do not know if DRBD is to blame for it at all. 

I never saw this problem with anything else than DRBD, though - this might
be because only DRBD was able to saturate the link for long enough for the 
problem to appear.

[ snip ]


peter




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