Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Andy, I see similar results for dd except the performance is even worse (approx 150MByte/s (connected) vs 780MByte/s (disconnected). It is possible you are seeing the same latency issue(s) I am and have posted about on this list in the last few days. title:[DRBD-user] High iowait on primary DRBD node with large sustained writes and replication enabled to secondary As Sebastian Riemer indicated in his comments on my blktrace analysis there is latency between the primary and secondary drbd nodes when the resource(s) is connected which does not exist when disconnected. Just what it is remains a mystery at this point in time. It probably involves either drbd and/or network latency on the primary and/or the secondary nodes. I have not had an opportunity to follow this up further yet. Sorry I can't be of much more help. Regards Paul > -----Original Message----- > From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user- > bounces at lists.linbit.com] On Behalf Of Andy Dills > Sent: Thursday, 10 January 2013 2:40 PM > To: drbd-user at lists.linbit.com > Subject: Re: [DRBD-user] Poor fsync performance > > On Tue, 8 Jan 2013, Andy Dills wrote: > > > # lvcreate -n test -L 10G data > > # mkfs.ext3 /dev/data/test > > # mount /dev/data/test /mnt > > # pveperf /mnt > > > > CPU BOGOMIPS: 95995.32 > > REGEX/SECOND: 838290 > > HD SIZE: 9.84 GB (/dev/mapper/data-test) > > BUFFERED READS: 477.27 MB/sec > > AVERAGE SEEK TIME: 5.87 ms > > FSYNCS/SECOND: 631.64 > > DNS EXT: 43.10 ms > > DNS INT: 1.18 ms > > > > The fsyncs/second should be tremendously higher. > > For what it's worth, here's what pveperf looks like with the resource > disconnected: > > # pveperf /mnt > CPU BOGOMIPS: 95997.00 > REGEX/SECOND: 877865 > HD SIZE: 9.84 GB (/dev/mapper/data-test) > BUFFERED READS: 465.67 MB/sec > AVERAGE SEEK TIME: 5.83 ms > FSYNCS/SECOND: 1691.68 > DNS EXT: 42.45 ms > DNS INT: 1.01 ms > > And here are some simple DD tests: > > Connected: > > # dd if=/dev/zero of=/mnt/file.tmp bs=512M count=1 oflag=direct > 1+0 records in > 1+0 records out > 536870912 bytes (537 MB) copied, 3.2879 s, 163 MB/s > > Disconnected: > > # dd if=/dev/zero of=/mnt/file.tmp bs=512M count=1 oflag=direct > 1+0 records in > 1+0 records out > 536870912 bytes (537 MB) copied, 1.54669 s, 347 MB/s > > > Any ideas why I'm seeing roughly 40% performance when my nodes are > connected? > > Thanks, > Andy > > --- > Andy Dills > Xecunet, Inc. > www.xecu.net > 301-682-9972 > --- > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user