[DRBD-user] Opteron/Xeon - Kernel 2.4/2.6 setup

Lars Ellenberg Lars.Ellenberg at linbit.com
Mon Jun 14 12:26:18 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.

/ 2004-06-14 11:57:04 +0200
\ Helmut Wollmersdorfer:
> Daniel Khan schrieb:
> >rsync has another disandavantage - it's consumes much CPU power on 
> >checking for updates.
> >I tried this once and I had massive load peaks.
> Try unison.
> Don't think, that CPU usage of DRBD is unimportant.
> During full sync with drbd on 600 MHz / 1200 BogoMips, 100 Mbit NIC, I 
> get total CPU usage of 50% (without it is "idle" at 0.5 - 1.5%, plain 
> IDE disks, no memory problems).

uhm, what does your cpu say to dd if=/dev/hda of=/dev/null ?
or to dd if=/dev/zero of=scratchfile ?

> This means, that I will hit the CPU 
> bottleneck at a sync-rate of 200 Mbit, before the PCI-Bus limit of 400 Mbit.

this is most likely NOT drbd consuming cpu, but _tcp_ used by drbd...
and might be reduced considerably by using NICs that do the tcp work
themselves (and nic drivers that are aware of it).
(and probably by using zero copy network writes as we do in 0.7)


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