Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hello Sebastian Thanks for the hint. The be sure that the settings are exactly the same on both sides, I wrote a script to set these settings by ssh on both nodes equally. So the current value for max_sectors_kb is: 64 on both nodes. But I played around with these values and nothing helped. When the nodes are connected, the write speed is even lower than in single node mode. I think there must be some kind of bottleneck between the blocksizes / ioscheduler, etc. and drbd but could find the igniting hint. Strange is also that the sync speed is very low (triggered manually resync to retest that) 66MB /s. All tests with different config settings showed no performance changement. blktrace also shows nothing more flashy which could lead to more. while resyncing and dd'ing the iostat shows 1.07% iowat which is imho very low value for a system under full io load. Is there a possibility to debug the network usage and internal network stats of drbd besides drbdsetup show 0? Regards Roland ----- Ursprüngliche Mail ----- Von: "Sebastian Riemer" <sebastian.riemer at profitbricks.com> An: "Roland Kaeser" <roland.kaeser at ziil.ch> CC: drbd-user at lists.linbit.com Gesendet: Mittwoch, 26. September 2012 15:49:07 Betreff: Re: [DRBD-user] Write performance again Hi Roland, I've analysed the DRBD 8.4.1 kernel code some time ago. DRBD has a dynamic IO request size detection which always starts at 4 KiB. If you've got a connection to the other system, then it negotiates a higher IO request size (128 KiB because of hashing functions). If you loose the connection, it's 4 KiB again. You can use the tool "blktrace" to trace how big the IO requests are. Or you can look at /sys/block/drbd0/queue/max_sectors_kb. IMHO this must become settable to the limits from the devices below if you already know that "max_sectors_kb" is completely equal on both sides. See: http://www.gossamer-threads.com/lists/drbd/users/24104 Cheers, Sebastian On 26.09.2012 14:50, Roland Kaeser wrote: > Only the drbd is very slow. (Single node, just to test write > perfomance on local block device. -- Ziil Informatiklösungen GmbH Roland Käser Leiter Technik Romanshornerstr. 134, CH-8280 Kreuzlingen Tel: +41 71 671 27 78 Fax: +41 71 671 27 79 www.ziil.ch -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20120926/17dc0e1c/attachment.htm>