[DRBD-user] very poor DRBD performance - what to check?

Christopher Grello chris at inetu.net
Fri Mar 20 15:10:03 CET 2009

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

> -----Original Message-----
> From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-
> bounces at lists.linbit.com] On Behalf Of Tobias Appel
> Sent: Friday, March 20, 2009 7:07 AM
> To: drbd-user at lists.linbit.com
> Subject: [DRBD-user] very poor DRBD performance - what to check?


> The question now is where can I start looking for the issue of this?

Disable the secondary node temporarily and run some basic throughput and latency tests on the primary node. For throughput:

  dd if=/dev/zero of=/var/tmp/4GBtestfile bs=512M count=8 oflag=direct

...and for latency:

  dd if=/dev/zero of=/var/tmp/testfile bs=512 count=100000 oflag=direct

It's a good idea to run them a couple of times each and average the results. You'll likely find that the disks are the bottleneck, but we'll see after you perform the tests. If you don't already have it, write-cache (battery-backed of course) is a great cost-effective way to increase I/O performance.

Christopher Grello
INetU Managed Hosting
Phone: (610) 266-7441
Toll-Free: (888) 664-6388
Fax: (610) 266-7434

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