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

Greg Freemyer greg.freemyer at gmail.com
Wed Oct 22 23:31:55 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.


On Tue, Oct 21, 2008 at 5:56 AM, Peter Sabaini <peter at sabaini.at> wrote:
> On Tuesday 21 October 2008 11:14:52 Bart Coninckx 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?
>>
>> These are the only benchmarks I know how to do on both DRBD and non-DRBD
>> partitions without destroying data.
>>
>> I actually care for both read and write performance obviously, since users
>> will be both reading and writing I guess (file and mailserver).
>>
>> What I just did is copying a 2.5 GB file to different locations. Mind you,
>> the file is on the same harddrive (on /). These are the results:
>>
>>
>> to ext3 filesystem on /dev/drbd0: 17MB/sec
>> to /opt (on the same LVM VG as drbd0): 20 MB/sec
>> to / (non LVM, non DRBD): 24 MB/sec
>>
>> So it seems there is a slight performance drop for DRBD, but the overall
>> performance is not that good.
>>
>> What is striking though, is that a scp to the other node results in a
>> performance of about 60 MB/sec.
>>
>> Is there any logical explanation for this? Is this because of my copy tests
>> read and write to the same drive? Can this explain the drop from about 60
>> MB/sec to about 20 MB/sec?
>
> Probably.
>
> I found it important to make very sure you know exactly what you are measuring
> before doing any test. In order to do this, try to measure isolated facts.
>
> Eg. to make certain you're measuring only read or write performance,
> use /dev/zero as a data source, respectively /dev/null as a target to
> eliminate interaction between parameters.
>

Recent versions of opensuse have a performance bug in /dev/zero, so
even that can cause a misleadingly low result.

Greg
-- 
Greg Freemyer
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
First 99 Days Litigation White Paper -
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com



More information about the drbd-user mailing list