[DRBD-user] 2nd try of reducing size...

[Christian Völker]

Hi all,

as I was (lucky!) able to recover from my firt failed attempt I'll give
it now a second try.

I have drbd 8.3 running on top of LVM.

I have already reduced the filesystem (ext3) size on the drbd0 device as
well as the drbd0 device itself (I suppose I have ;-)). My last attempt
to reduce the LVM backing device ended up in I/O errors for drbd :(

So as I said I've already reduced the drbd (with the reduce command) and
it's running fine:
[root at drbd ~]# cat /proc/drbd
version: 8.3.12 (api:88/proto:86-96)
GIT-hash: e2a8ef4656be026bbae540305fcb998a5991090f build by
dag at Build64R6, 2011-11-20 10:57:03
 0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate A r-----
    ns:0 nr:2147352908 dw:2147352908 dr:0 al:0 bm:131064 lo:0 pe:0 ua:0
ap:0 ep:1 wo:d oos:0

And the filesystem is at a smaller size, too. The e2fsck (including bad
blocks check) runs fine without errors.

So I assume everything here is everything fine so far and I should able
to reduce the backing device, shouldn't I?

How does LVM know which blocks to free upon reduce? In other words how
does LVM know which blocks are not in use by drbd?

Thanks

Christian