Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On 01/24/2012 10:59 AM, samppah at neutraali.net wrote: > Hello all, > > I'm running DRBD on two following machines: > Scientific Linux 6.1 > Intel Xeon E5620 Quad Core > 12GB Ram > LSI 9280-4i4e + CacheCade 1.0 (CacheCade is currently disabled) > 12x 1TB Seagate Constellation SAS 7200 RPM drives > > DRBD has been configured in master/slave -fashion and there is 10 GbE > dedicated link between machines for DRBD traffic. > Drives have been configured in RAID-10 mode with 64 kB Stripe Size. > > DRBD version is 8.4.0 (api:1/proto:86-100). Have you tried to reproduce that with drbd 8.4.1 ? Regards, Andreas -- Need help with DRBD? http://www.hastexo.com/now > > Couple of weeks ago I had to do some maintenance work on node1 (normally > the master node) so I moved all services to run on node2. Everything > went well and since machines are identical I didn't bother to move > services back to node1. Few days later I noticed that performance was > somewhat degraded but difference was so minimal that I didn't focus on > it at all. > > A little later I was asked to do some simple read performance tests. > Everything looked ok when doing direct reads on DRBD-device: > > dd if=/dev/drbd0 of=/dev/null bs=1M iflag=direct > ^C17317+0 records in > 17316+0 records out > 18157142016 bytes (18 GB) copied, 21.3465 s, 851 MB/s > > But with buffered reads things get slow: > > dd if=/dev/drbd0 of=/dev/null bs=1M > ^C11131+0 records in > 11130+0 records out > 11670650880 bytes (12 GB) copied, 105.299 s, 111 MB/s > > However, the underlying disk seems to be fine: > > dd if=/dev/sdb of=/dev/null bs=1M > ^C14087+0 records in > 14086+0 records out > 14770241536 bytes (15 GB) copied, 19.8579 s, 744 MB/s > > I moved services back to node1 and the problem was gone (dd > if=/dev/drbd0 of=/dev/null bs=1M, 37312528384 bytes (37 GB) copied, > 54.8519 s, 680 MB/s). Now I started to investigate what caused the > issues and moved services to node2 and performance problems hit again so > I thought that there has to be something wrong on node2. I compared > settings between the two machines to make sure they are really identical > and found nothing strange between them. Raid sets are fine and there are > no error messages in log files. At this point I decided to reboot node1 > and after that moved services back to it. After the reboot performance > dropped also on node1 and I haven't been able to find out anything that > could really help getting performance up again. > > So it seems like DRBD has huge effect when it comes to buffered reads. > It may very well be that I have forgotten to do some sysctl or such > tuning after reboot but I can't figure out what it could be. Any ideas > how to work this out or is this expected behaviour? > > I'm currently using following settings on my disks: > > echo deadline > /sys/block/sdb/queue/scheduler > echo 0 > /sys/block/sdb/queue/iosched/front_merges > echo 150 > /sys/block/sdb/queue/iosched/read_expire > echo 1500 > /sys/block/sdb/queue/iosched/write_expire > echo 32000000 > /proc/sys/vm/dirty_background_bytes > echo 384000000 > /proc/sys/vm/dirty_bytes > echo 1024 > /sys/block/sdb/queue/nr_requests > > and current DRBD resource configuration: > > resource drbd0 { > device /dev/drbd0; > disk /dev/sdb1; > meta-disk internal; > > options { > cpu-mask 15; > } > > net { > protocol C; > max-buffers 8000; > max-epoch-size 8000; > unplug-watermark 16; > sndbuf-size 0; > } > > disk { > al-extents 3389; > disk-barrier no; > disk-flushes no; > } > > on node1 { > address 10.10.10.1:7789; > } > on node2 { > address 10.10.10.2:7789; > } > } > > Best regards, > Samuli Heinonen > > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 222 bytes Desc: OpenPGP digital signature URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20120124/8a169cbf/attachment.pgp>