[DRBD-user] MySQL-over-DRBD Performance

Lars Ellenberg lars.ellenberg at linbit.com
Thu Dec 20 12:05:25 CET 2007

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

On Wed, Dec 19, 2007 at 04:41:37PM -0800, Art Age Software wrote:
> I have run some additional tests:
> 1) Disabled bonding on the network interfaces (both nodes). No
> significant change.
> 2) Changed the DRBD communication interface. Was using a direct
> crossover connection between the on-board NICs of the servers. I
> switched to Intel Gigabit NIC cards in both machines, connecting
> through a Gigabit switch. No significant change.
> 3) Ran a file copy from node1 to node2 via scp. Even with the
> additional overhead of scp, I get a solid 65 MB/sec. throughput.

this is streaming.
completely different than what we measured below.

> So, at this stage I have seemingly ruled out:
> 1) Slow IO subsystem (both machines measured and check out fine).
> 2) Bonding driver (additional latency)
> 3) On-board  NICs (hardware/firmware problem)
> 4) Network copy speed.
> What's left?  I'm stumped as to why DRBD can only do about 3.5 BM/sec.
> on this very fast hardware.

doing one-by-one synchronous 4k writes, which are latency bound.
if you do streaming writes, it probably get up to your 65 MB/sec again.

sorry, latency tuning can be complex,
and is not easily covered by "general advice".

: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
: LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
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