[DRBD-user] drbd resource write performance and sync speeds

Ralf Gross Ralf-Lists at ralfgross.de
Wed Apr 9 10:49:57 CEST 2008

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


Christian Balzer schrieb:
> > If your local I/O subsystem pulls 120MB/s, the expected max DRBD
> > throughput is around 105 MB/s:
> > 
> > - disk does 120,
> > - Gigabit Ethernet realistically does 110,
> Yeah, various network tests get near that value.
> 
> > - so the network is your bottleneck,
> It's a bonded dual GigE. Initially done to give DRBD enough breathing room
> and left in place to have more redundancy for it and heartbeat.

Are the servers directly connected or are you using switch to connect?
I tried the round-robin bonding mode with cisco switches, but cisco
doesn't support rr mode. At least when I tested it. So in the end the
connection between my 2 server was still limited by a single GbE link.

In a test with 2 x GbE crossover connections, I was able to achive
~170 MB/s with the netpipe benchmark. I didn't test this with drbd,
but other daemons (smbd, vsftp) didn't show a huge impovement from his
raw speed gain. The limit was always ~80 MB/s.

Ralf



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