[DRBD-user] drbd turned on me, and bit my hand this morn

Lars Ellenberg Lars.Ellenberg at linbit.com
Tue Dec 6 19:46:35 CET 2005

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

/ 2005-12-06 13:17:25 -0500
\ Brad Barnett:

> > how much storage?
> 1.2T

so it needs to do meta data io for about 40 MB.
it does so using synchronous io for each 512 byte sector.
so it has to do about 70 thousand syncronous io operations...
that may take some time, especially if something else runs on the box,
or your io-scheduler is "too intelligent".

I don't know how long, though.
typically it should not take much more than a few minutes.
we at LINBIT use DRBD-plus for that storage sizes, where "drbdadm up"
succeeds within a few seconds even on several TB storage.

to verify whether drbd is indeed "hung" or just slooowly initilizing for
that storage size, you could
 watch -n1 cat /proc/partitions
and watch the read/write figures for the lower level device.

> At one point, I changed the config file to 10 seconds, for every time
> listed there (including the wfc-timeout mentioned by Diego).  It didn't
> seem to time out, and I waited for quite some time (at least 5 minutes).

these timeouts are all not active, yet.
your setup "apears to be hung" during device initialization.
and it may well be that your lower level storage device is just slooow
for sector-sized synchronous access.

> I would modprobe the drbd module manually.

> I still don't understand why it always shows two drbd devices though. :/

because, if you modprobe it manually, it defaults to "minor_count=2".

if you let the script to it, it will count the number of actually used
resources in the drbd.conf, and uses that value there; unless overridden
by an entry in the global {} section.

: Lars Ellenberg                                  Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH            Fax +43-1-8178292-82 :
: Schoenbrunner Str. 244, A-1120 Vienna/Europe   http://www.linbit.com :
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