[DRBD-user] blocking I/O with drbd

Volker mail at blafoo.org
Fri Dec 16 14:45:58 CET 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


>  have you tried with elevator=deadline?
>  what does "cat /sys/block/dm-*/queue/scheduler" show?

i did a couple of days ago, but just tried it again:

For the '/sys/block/dm-[0,1,2]' i do not have a scheduler-file. Only for


This link at heading 16.3.3 fully describes what just tried:


Here are the currently active settings:

/sys/block/sdb/queue/scheduler => noop anticipatory [deadline] cfq

/sys/block/sdb/queue/iosched/write_expire => 1500

/sys/block/sdb/queue/iosched/read_expire => 150

/sys/block/sdb/queue/iosched/front_merges => 0

Im sorry to report, that did not change a thing. dd with oflag=direct is
still slow and without the flag the load still jumps through the roof.

What surprises me the most is the delay between the load rising and the
finished dd. a short timeline to make myself clear:

01:00:00  load 0.5-1
01:00:00  dd if=/dev/zero of=./test-data.dd bs=4096 count=10240
01:00:01  dd finished successfully
01:00:05  load 0.5-1
01:00:10  load 2.5-3
01:00:18  load 3.5-4
01:00:22  load 3.0-3.5
01:00:45  load 2.8
01:01:00  load 1.7
01:01:10  load 1.5
01:01:30  load 1.2
01:02:00  load 0.8


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