[DRBD-user] drbd 8.2.1 partially hanging when writing lots of data

Michael Nelson mikenel at gmail.com
Thu Dec 27 22:33:44 CET 2007

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

> >do NOT "force sync" if you "get stuck" during normal operation.
> t>hat is just nonsense.

I wouldn't do that normally, I just wanted to see if it that would change
the behavior.

> would be interessting to find out where exactly it hangs.
> if these are still responsive to the console,
> try to get a process list while it "hangs":
> ps -eo pid,state,wchan:40,comm | grep -e "[d]rbd" -e D

On the sender side:

 4472 S -                                        drbd0_worker
 4487 S -                                        drbd0_receiver
 4488 S -                                        drbd0_asender
 4659 D blk_congestion_wait                      dd

Every once in a while it will block on pdflush. But mostly it waits on dd.

My current dd command is:

dd if=/dev/zero of=foo bs=512k count=2048

Also, I am using a loop device underneath DRBD to test this, not a raw drive
or LVM.

> this is likely too high if you have only 512 MB RAM.
> try with max-buffers 4000, max-epoch-size 4000 or less.

Ok, I have adjusted it back to 4000.

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