[DRBD-user] sync rate seems low

Monty Taylor mtaylor at mysql.com
Wed Aug 9 01:12:27 CEST 2006

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

I agree, that's what it seems like. But then I ran iperf on the
interface and got this:

[  3] local port 32810 connected with port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.08 GBytes   929 Mbits/sec

Which is more like what I'd expect to see. On the interface. So why is
DRBD only seeing 100M while the interface can support and is running
at 1G?


On 8/8/06, Vampire D <vampired at gmail.com> wrote:
> Well first off, I doubt you will be any where near 125M sync rate, that's
> 125MB/s if I am not mistaken.  I run GBit connections and I only have a sync
> rate of around 60M.
> 2nd, 100Mbit caps at around 12MB/s throughput and 10Mbit is roughly 1.2Mb/s
> so it is definately at 100Mbit.  But 8Mbit isn't all that bad for 100Mbit,
> it is only 2/3rds of the capacity of your network interface, so I assume
> your disk sub system is your bottleneck one way or another.  Try benching
> your drives with timed dd or use some bench tool.
> With two raptors and Gbit ethernet cross over cabled, I get around 56Mb/s
> but I haven't been able to test the sync rate since the initial sync and no
> one seems to have an answer to easily test that after the drbd is
> consisitent.
> On 8/8/06, Monty Taylor <mtaylor at mysql.com> wrote:
> >
> Hey all,
> I'm rolling out a DRBD at the moment and I'm getting much lower
> initial sync rate than I would expect. I have the two machines
> connected with crossover cables and the rate set at 125M, but I'm only
> seeing 8M/sec of transfer rate.
> I'm sure I'm missing something stupid, but I've rolled DRBD out
> several times over the past couple of months and never had this
> problem. Anybody have an idea of something I can check?
> Thanks,
> Monty
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> just like the criminal they are playing?"
> Christopher

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