Hmm, perhaps there's a secondary bug.
Can you send the output from strace, i.e. strace.log after running:
cat snap1.diff | strace -f -o strace.log rbd merge-diff - snap2.diff
combined.diff
for a case where it fails?
Josh
On 12/09/2015 08:38 PM, Alex Gorbachev wrote:
More oddity: retrying several times, the merge-diff sometimes works and
sometimes does not, using the same source files.
On Wed, Dec 9, 2015 at 10:15 PM, Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx
<mailto:ag@xxxxxxxxxxxxxxxxxxx>> wrote:
Hi Josh, looks like I celebrated too soon:
On Wed, Dec 9, 2015 at 2:25 PM, Josh Durgin <jdurgin@xxxxxxxxxx
<mailto:jdurgin@xxxxxxxxxx>> wrote:
This is the problem:
http://tracker.ceph.com/issues/14030
As a workaround, you can pass the first diff in via stdin, e.g.:
cat snap1.diff | rbd merge-diff - snap2.diff combined.diff
one test worked - merging the initial full export (export-diff with
just one snapshot)
but the second one failed (merging two incremental diffs):
root@lab2-b1:/data/volume1# cat scrun1-120720151502.bck | rbd
merge-diff - scrun1-120720151504.bck scrun1-part04.bck
Merging image diff: 13% complete...failed.
rbd: merge-diff error
I am not sure how to run gdb in such scenario with stdin/stdout
Thanks,
Alex
Josh
On 12/08/2015 11:11 PM, Josh Durgin wrote:
On 12/08/2015 10:44 PM, Alex Gorbachev wrote:
Hi Josh,
On Mon, Dec 7, 2015 at 6:50 PM, Josh Durgin
<jdurgin@xxxxxxxxxx <mailto:jdurgin@xxxxxxxxxx>
<mailto:jdurgin@xxxxxxxxxx <mailto:jdurgin@xxxxxxxxxx>>>
wrote:
On 12/07/2015 03:29 PM, Alex Gorbachev wrote:
When trying to merge two results of rbd
export-diff, the
following error
occurs:
iss@lab2-b1:~$ rbd export-diff --from-snap
autosnap120720151500
spin1/scrun1@autosnap120720151502
/data/volume1/scrun1-120720151502.bck
iss@lab2-b1:~$ rbd export-diff --from-snap
autosnap120720151504
spin1/scrun1@autosnap120720151504
/data/volume1/scrun1-120720151504.bck
iss@lab2-b1:~$ rbd merge-diff
/data/volume1/scrun1-120720151502.bck
/data/volume1/scrun1-120720151504.bck
/data/volume1/mrg-scrun1-0204.bck
Merging image diff: 11% complete...failed.
rbd: merge-diff error
That's all the output and I have found this link
http://tracker.ceph.com/issues/12911 but not sure if the
patch
should
have already been in hammer or how to get it?
That patch fixed a bug that was only present after
hammer, due to
parallelizing export-diff. You're likely seeing a
different (possibly
new) issue.
Unfortunately there's not much output we can enable for
export-diff in
hammer. Could you try running the command via gdb
to figure out where
and why it's failing? Make sure you have librbd-dbg
installed, then
send the output from gdb doing:
gdb --args rbd merge-diff
/data/volume1/scrun1-120720151502.bck \
/data/volume1/scrun1-120720151504.bck
/data/volume1/mrg-scrun1-0204.bck
break rbd.cc:1931
break rbd.cc:1935
break rbd.cc:1967
break rbd.cc:1985
break rbd.cc:1999
break rbd.cc:2008
break rbd.cc:2021
break rbd.cc:2053
break rbd.cc:2098
run
# (it will run now, stopping when it hits the error)
info locals
Will do - how does one load librbd-dbg? I have the
following on the
system:
librbd-dev - RADOS block device client library
(development files)
librbd1-dbg - debugging symbols for librbd1
is librbd1-dbg sufficient?
Yes, I just forgot the 1 in the package name.
Also a question - the merge-diff really stitches the to
diff files
together, not really merges, correct? For example, in
the following
workflow:
export-diff from full image - 10GB
export-diff from snap1 - 2 GB
export-diff from snap2 - 1 GB
My resulting merge export file would be 13GB, correct?
It does merge overlapping sections, i.e. part of snap1 that was
overwritten in snap2, so the merged diff may be smaller than the
original two.
Josh
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