On 09/14/2016 05:53 PM, Ilya Dryomov wrote:
> On Wed, Sep 14, 2016 at 3:30 PM, Nikolay Borisov <kernel@xxxxxxxx> wrote:
>>
>>
>> On 09/14/2016 02:55 PM, Ilya Dryomov wrote:
>>> On Wed, Sep 14, 2016 at 9:01 AM, Nikolay Borisov <kernel@xxxxxxxx> wrote:
>>>>
>>>>
>>>> On 09/14/2016 09:55 AM, Adrian Saul wrote:
>>>>>
>>>>> I found I could ignore the XFS issues and just mount it with the appropriate options (below from my backup scripts):
>>>>>
>>>>> #
>>>>> # Mount with nouuid (conflicting XFS) and norecovery (ro snapshot)
>>>>> #
>>>>> if ! mount -o ro,nouuid,norecovery $SNAPDEV /backup${FS}; then
>>>>> echo "FAILED: Unable to mount snapshot $DATESTAMP of $FS - cleaning up"
>>>>> rbd unmap $SNAPDEV
>>>>> rbd snap rm ${RBDPATH}@${DATESTAMP}
>>>>> exit 3;
>>>>> fi
>>>>> echo "Backup snapshot of $RBDPATH mounted at: /backup${FS}"
>>>>>
>>>>> It's impossible without clones to do it without norecovery.
>>>>
>>>> But shouldn't freezing the fs and doing a snapshot constitute a "clean
>>>> unmount" hence no need to recover on the next mount (of the snapshot) -
>>>> Ilya?
>>>
>>> I *thought* it should (well, except for orphan inodes), but now I'm not
>>> sure. Have you tried reproducing with loop devices yet?
>>
>> Here is what the checksum tests showed:
>>
>> fsfreeze -f /mountpoit
>> md5sum /dev/rbd0
>> f33c926373ad604da674bcbfbe6460c5 /dev/rbd0
>> rbd snap create xx@xxx && rbd snap protect xx@xxx
>> rbd map xx@xxx
>> md5sum /dev/rbd1
>> 6f702740281874632c73aeb2c0fcf34a /dev/rbd1
>>
>> where rbd1 is a snapshot of the rbd0 device. So the checksum is indeed
>> different, worrying.
>
> Sorry, for the filesystem device you should do
>
> md5sum <(dd if=/dev/rbd0 iflag=direct bs=8M)
>
> to get what's actually on disk, so that it's apples to apples.
root@alxc13:~# rbd showmapped |egrep "device|c11579"
id pool image snap device
47 rbd c11579 - /dev/rbd47
root@alxc13:~# fsfreeze -f /var/lxc/c11579
root@alxc13:~# md5sum <(dd if=/dev/rbd47 iflag=direct bs=8M)
12800+0 records in
12800+0 records out
107374182400 bytes (107 GB) copied, 617.815 s, 174 MB/s
2ddc99ce1b3ef51da1945d9da25ac296 /dev/fd/63 <--- Check sum after freeze
root@alxc13:~# rbd snap create rbd/c11579@snap_test
root@alxc13:~# rbd map c11579@snap_test
/dev/rbd1
root@alxc13:~# md5sum <(dd if=/dev/rbd1 iflag=direct bs=8M)
12800+0 records in
12800+0 records out
107374182400 bytes (107 GB) copied, 610.043 s, 176 MB/s
2ddc99ce1b3ef51da1945d9da25ac296 /dev/fd/63 <--- Check sum of snapshot
root@alxc13:~# md5sum <(dd if=/dev/rbd47 iflag=direct bs=8M)
12800+0 records in
12800+0 records out
107374182400 bytes (107 GB) copied, 592.164 s, 181 MB/s
2ddc99ce1b3ef51da1945d9da25ac296 /dev/fd/63 <--- Check sum of original device, not changed - GOOD
root@alxc13:~# file -s /dev/rbd1
/dev/rbd1: Linux rev 1.0 ext4 filesystem data (extents) (large files) (huge files)
root@alxc13:~# fsfreeze -u /var/lxc/c11579
root@alxc13:~# md5sum <(dd if=/dev/rbd47 iflag=direct bs=8M)
12800+0 records in
12800+0 records out
107374182400 bytes (107 GB) copied, 647.01 s, 166 MB/s
92b7182591d7d7380435cfdea79a8897 /dev/fd/63 <--- After unfreeze checksum is different - OK
root@alxc13:~# md5sum <(dd if=/dev/rbd1 iflag=direct bs=8M)
12800+0 records in
12800+0 records out
107374182400 bytes (107 GB) copied, 590.556 s, 182 MB/s
bc3b68f0276c608d9435223f89589962 /dev/fd/63 <--- Why the heck the checksum of the snapshot is different after unfreeze? BAD?
root@alxc13:~# file -s /dev/rbd1
/dev/rbd1: Linux rev 1.0 ext4 filesystem data (needs journal recovery) (extents) (large files) (huge files)
root@alxc13:~#
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