Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Thursday 23 October 2008 12:00, drbd-user-request at lists.linbit.com wrote: > 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 Yeah, heard before about that. This time I used a another test/benchmark for comparison. I scp-ied a 2.5 GB file to / (normal partition), /opt (on LVM) and /data (on DRBD on same LVM). It seems that DRBD is half as slow as the other copies, which encourages me to think that DRBD is the culprit. The underlying disk is the same and the network link for DRBD works full speed, so there's obviously something wrong with the DRBD setup IMHO. Is this a correct assumption? B.