[DRBD-user] Re: drbd is performing at 12 MB/sec on recent

Andrew Armstrong aarmstrong at tsbrass.com
Mon Oct 20 14:01:36 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.

Sorry for the aside on this, but this info might be helpful for anyone
who is using SLES10 SP2 and testing performance using /dev/zero.
I have noticed extreme drops in output from /dev/zero on any SP2
kernel. This has actually been confirmed by Novell support... Evidently
the SLES programmers in Germany changed some of the properties of
/dev/zero to fix "other memory issues". According to them, /dev/zero is
no longer a good measurement of throughput. Supposedly, the programmers
are looking into restoring /dev/zero output performance levels, but
their comment was "no one uses /dev/zero for REAL performance testing
these days".
Here is a good example:
On a HP DL365 with 32GB of RAM, the following test: ( dd if=/dev/zero
of=/dev/null bs=1G count=1 ) produced an output of 28GB/sec on SP1 and
700MB/sec on SP2. I also noticed performance differences on output to
raid hardware, but don't have those numbers. 

Andrew Armstrong

>>> On 10/20/2008 at 6:33 AM, in message
<20081020103350.GA10572 at soda.linbit>, Lars Ellenberg
<lars.ellenberg at linbit.com> wrote:
On Sat, Oct 18, 2008 at 09:18:33PM +0200, Petersen, Joerg wrote:
> Well, my experience is that 8.0.7 is the fastest DRDB...
> Later Versions just got slower!
> Try: no-disk-flushes
> and: no-md-flushes
> if you are using DRBD >= 8.0.13
> Not completely same to 8.0.7 but near to it...

to recommend a known buggy version for imagined performance reasons is
not particular HA.

> Hi Lars,
> I did these:
> node1:/opt # hdparm -t /dev/drbd0

> Do these tests make any sence?

if you care for write performance,
why are you doing read benchmarks?

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com 

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