Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Am Donnerstag 02 September 2010 schrieb Lars Ellenberg: > > Starvation probably happens on the Secondary. > It should vanish if you > echo 1 > /sys/modules/drbd/parameters/disable_sendpage > Starvation is gone with disabled sendpage feature! [secondary]# cat /sys/module/drbd/parameters/disable_sendpage Y [diskless primary]# dd if=/dev/drbd0 of=/dev/null iflag=direct bs=9M count=50 50+0 records in 50+0 records out 471859200 bytes (472 MB) copied, 4.91869 seconds, 95.9 MB/s I did not see any performance degradation not using sendpage with 1Gbit Link between Primary and Secondary (works like a charm;-). Does using sendpage makes a difference when it comes to >= 10Gbit Links? > As long as you have _occasional_ write requests while you do the > sequential read, you should still be fine, too. > Doing writes during big direct io reads does _not_ fix it: I run this in background to produce about 10 writes/sec: while :; do date --iso-8601=sec; dd if=/dev/zero of=/dev/drbd0 bs=1k count=1 conv=fsync 2> /dev/null; sleep .1; done But direct io reads are still stucked (and the writes also get stucked): # dd if=/dev/drbd0 of=/dev/null iflag=direct bs=9M count=50 50+0 records in 50+0 records out 471859200 bytes (472 MB) copied, 163.932 seconds, 2.9 MB/s Kind Regards, Roland -- Roland.Friedwagner at wu.ac.at Phone: +43 1 31336 5377 IT Services - WU (Vienna University of Economics and Business)