Shinobu
On Wed, Sep 9, 2015 at 4:31 PM, Goncalo Borges
<goncalo@xxxxxxxxxxxxxxxxxxx <mailto:goncalo@xxxxxxxxxxxxxxxxxxx>> wrote:
Dear Ceph / CephFS gurus...
Bare a bit with me while I give you a bit of context. Questions
will appear at the end.
1) I am currently running ceph 9.0.3 and I have install it to
test the cephfs recovery tools.
2) I've created a situation where I've deliberately (on purpose)
lost some data and metadata (check annex 1 after the main email).
3) I've stopped the mds, and waited to check how the cluster
reacts. After some time, as expected, the cluster reports a ERROR
state, with a lot of PGs degraded and stuck
# ceph -s
cluster 8465c6a6-5eb4-4cdf-8845-0de552d0a738
health HEALTH_ERR
174 pgs degraded
48 pgs stale
174 pgs stuck degraded
41 pgs stuck inactive
48 pgs stuck stale
238 pgs stuck unclean
174 pgs stuck undersized
174 pgs undersized
recovery 22366/463263 objects degraded (4.828%)
recovery 8190/463263 objects misplaced (1.768%)
too many PGs per OSD (388 > max 300)
mds rank 0 has failed
mds cluster is degraded
monmap e1: 3 mons at
{mon1=X.X.X.X:6789/0,mon2=Y.Y.Y.Y:6789/0,mon3=Z.Z.Z.Z:6789/0}
election epoch 10, quorum 0,1,2 mon1,mon3,mon2
mdsmap e24: 0/1/1 up, 1 failed
osdmap e544: 21 osds: 15 up, 15 in; 87 remapped pgs
pgmap v25699: 2048 pgs, 2 pools, 602 GB data, 150 kobjects
1715 GB used, 40027 GB / 41743 GB avail
22366/463263 objects degraded (4.828%)
8190/463263 objects misplaced (1.768%)
1799 active+clean
110 active+undersized+degraded
60 active+remapped
37 stale+undersized+degraded+peered
23 active+undersized+degraded+remapped
11 stale+active+clean
4 undersized+degraded+peered
4 active
4) I've umounted the cephfs clients ('umount -l' worked for me
this time but I already had situations where 'umount' would simply
hang, and the only viable solutions would be to reboot the client).
5) I've recovered the ceph cluster by (details on the recover
operations are in annex 2 after the main email.)
- declaring the osds lost
- removing the osds from the crush map
- letting the cluster stabilize and letting all the recover I/O finish
- identifying stuck PGs
- checking if they existed, and if not recreate them.
6) I've restarted the MDS. Initially, the mds cluster was
considered degraded but after some small amount of time, that
message disappeared. The WARNING status was just because of "too
many PGs per OSD (409 > max 300)"
# ceph -s
cluster 8465c6a6-5eb4-4cdf-8845-0de552d0a738
health HEALTH_WARN
too many PGs per OSD (409 > max 300)
mds cluster is degraded
monmap e1: 3 mons at
{mon1=X.X.X.X:6789/0,mon2=Y.Y.Y.Y:6789/0,mon3=Z.Z.Z.Z:6789/0}
election epoch 10, quorum 0,1,2 mon1,mon3,mon2
mdsmap e27: 1/1/1 up {0=rccephmds=up:reconnect}
osdmap e614: 15 osds: 15 up, 15 in
pgmap v27304: 2048 pgs, 2 pools, 586 GB data, 146 kobjects
1761 GB used, 39981 GB / 41743 GB avail
2048 active+clean
client io 4151 kB/s rd, 1 op/s
(wait some time)
# ceph -s
cluster 8465c6a6-5eb4-4cdf-8845-0de552d0a738
health HEALTH_WARN
too many PGs per OSD (409 > max 300)
monmap e1: 3 mons at
{mon1=X.X.X.X:6789/0,mon2=Y.Y.Y.Y:6789/0,mon3=Z.Z.Z.Z:6789/0}
election epoch 10, quorum 0,1,2 mon1,mon3,mon2
mdsmap e29: 1/1/1 up {0=rccephmds=up:active}
osdmap e614: 15 osds: 15 up, 15 in
pgmap v30442: 2048 pgs, 2 pools, 586 GB data, 146 kobjects
1761 GB used, 39981 GB / 41743 GB avail
2048 active+clean
7) I was able to mount the cephfs filesystem in a client. When I
tried to read a file made of some lost objects, I got holes in
part of the file (compare with the same operation on annex 1)
# od /cephfs/goncalo/5Gbytes_029.txt | head
0000000 000000 000000 000000 000000 000000 000000 000000 000000
*
2000000 176665 053717 015710 124465 047254 102011 065275 123534
2000020 015727 131070 075673 176566 047511 154343 146334 006111
2000040 050506 102172 172362 121464 003532 005427 137554 137111
2000060 071444 052477 123364 127652 043562 144163 170405 026422
2000100 050316 117337 042573 171037 150704 071144 066344 116653
2000120 076041 041546 030235 055204 016253 136063 046012 066200
2000140 171626 123573 065351 032357 171326 132673 012213 016046
2000160 022034 160053 156107 141471 162551 124615 102247 125502
Finally the questions:
a./ Under a situation as the one describe above, how can we safely
terminate cephfs in the clients? I have had situations where
umount simply hangs and there is no real way to unblock the
situation unless I reboot the client. If we have hundreds of
clients, I would like to avoid that.
b./ I was expecting to have lost metadata information since I've
clean OSDs where metadata information was stored for the
/cephfs/goncalo/5Gbytes_029.txt file. I was a bit surprised that
the /'cephfs/goncalo/5Gbytes_029.txt' was still properly
referenced, without me having to run any recover tool. What am I
missing?
c./ After recovering the cluster, I though I was in a cephfs
situation where I had
c.1 files with holes (because of lost PGs and objects in the
data pool)
c.2 files without metadata (because of lost PGs and objects in
the metadata pool)
c.3 metadata without associated files (because of lost PGs and
objects in the data pool)
I've tried to run the recovery tools, but I have several doubts
which I did not found described in the documentation
- Is there a specific order / a way to run the tools for the
c.1, c.2 and c.3 cases I mentioned?
d./ Since I was testing, I simply ran the following sequence but I
am not sure of what the command are doing, nor if the sequence is
correct. I think an example use case should be documented.
Specially the cephfs-data-scan did not returned any output, or
information. So, I am not sure if anything happened at all.
# cephfs-table-tool 0 reset session
{
"0": {
"data": {},
"result": 0
}
}
# cephfs-table-tool 0 reset snap
{
"result": 0
}
# cephfs-table-tool 0 reset inode
{
"0": {
"data": {},
"result": 0
}
}
# cephfs-journal-tool --rank=0 journal reset
old journal was 4194304~22381701
new journal start will be 29360128 (2784123 bytes past old end)
writing journal head
writing EResetJournal entry
done
# cephfs-data-scan init
# cephfs-data-scan scan_extents cephfs_dt
# cephfs-data-scan scan_inodes cephfs_dt
# cephfs-data-scan scan_extents --force-pool cephfs_mt
(doesn't seem to work)
e./ After running the cephfs tools, everything seemed exactly in
the same status. No visible changes or errors at the filesystem
level. So, at this point not sure what to conclude...
Thank you in Advance for your responses
Cheers
Goncalo
# #####################
# ANNEX 1: GENERATE DATA LOSS #
# #####################
1) Check a file
# ls -l /cephfs/goncalo/5Gbytes_029.txt
-rw-r--r-- 1 root root 5368709120 Sep 8 03:55
/cephfs/goncalo/5Gbytes_029.txt
--- * ---
2) See its contents
# od /cephfs/goncalo/5Gbytes_029.txt | head
0000000 150343 117016 156040 100553 154377 174521 137643 047440
0000020 006310 013157 064422 136662 145623 116101 137007 031237
0000040 111570 010104 103540 126335 014632 053445 006114 047003
0000060 123201 170045 042771 036561 152363 017716 000405 053556
0000100 102524 106517 066114 071112 144366 011405 074170 032621
0000120 047761 177217 103414 000774 174320 122332 110323 065706
0000140 042467 035356 132363 067446 145351 155277 177533 062050
0000160 016303 030741 066567 043517 172655 176016 017304 033342
0000200 177440 130510 163707 060513 055027 107702 023012 130435
0000220 022342 011762 035372 044033 152230 043424 004062 177461
--- * ---
3) Get its inode, and convert it to HEX
# ls -li /cephfs/goncalo/5Gbytes_029.txt
1099511627812 -rw-r--r-- 1 root root 5368709120 Sep 8 03:55
/cephfs/goncalo/5Gbytes_029.txt
(1099511627812)_base = (10000000024)_base16
--- * ---
4) Get the osd pool details
# ceph osd pool ls detail
pool 1 'cephfs_dt' replicated size 3 min_size 2 crush_ruleset 0
object_hash rjenkins pg_num 1024 pgp_num 1024 last_change 196
flags hashpspool crash_replay_interval 45 stripe_width 0
pool 2 'cephfs_mt' replicated size 3 min_size 2 crush_ruleset 0
object_hash rjenkins pg_num 1024 pgp_num 1024 last_change 182
flags hashpspool stripe_width 0
--- * ---
5) Get the file / PG / OSD mapping
# ceph osd map cephfs_dt 10000000024.00000000
osdmap e479 pool 'cephfs_dt' (1) object '10000000024.00000000' ->
pg 1.c18fbb6f (1.36f) -> up ([19,15,6], p19) acting ([19,15,6], p19)
# ceph osd map cephfs_mt 10000000024.00000000
osdmap e479 pool 'cephfs_mt' (2) object '10000000024.00000000' ->
pg 2.c18fbb6f (2.36f) -> up ([27,23,13], p27) acting ([27,23,13], p27)
--- * ---
6) Kill the relevant osd daemons, umount the osd partition and
delete the partitions
[root@server1 ~]# for o in 6; do dev=`df /var/lib/ceph/osd/ceph-$o
| tail -n 1 | awk '{print $1}'`; /etc/init.d/ceph stop osd.$o;
umount /var/lib/ceph/osd/ceph-$o; parted -s ${dev::8} rm 1; parted
-s ${dev::8} rm 2; partprobe; done
[root@server2 ~]# for o in 13 15; do dev=`df
/var/lib/ceph/osd/ceph-$o | tail -n 1 | awk '{print $1}'`;
/etc/init.d/ceph stop osd.$o; umount /var/lib/ceph/osd/ceph-$o;
parted -s ${dev::8} rm 1; parted -s ${dev::8} rm 2; partprobe; done
[root@server3 ~]# for o in 19 23; do dev=`df
/var/lib/ceph/osd/ceph-$o | tail -n 1 | awk '{print $1}'`;
/etc/init.d/ceph stop osd.$o; umount /var/lib/ceph/osd/ceph-$o;
parted -s ${dev::8} rm 1; parted -s ${dev::8} rm 2; partprobe; done
[root@server4 ~]# for o in 27; do dev=`df
/var/lib/ceph/osd/ceph-$o | tail -n 1 | awk '{print $1}'`;
/etc/init.d/ceph stop osd.$o; umount /var/lib/ceph/osd/ceph-$o;
parted -s ${dev::8} rm 1; parted -s ${dev::8} rm 2; partprobe; done
# #######################
# ANNEX 2: RECOVER CEPH CLUSTER #
# #######################
1) Declare OSDS losts
# for o in 6 13 15 19 23 27;do ceph osd lost $o
--yes-i-really-mean-it; done
marked osd lost in epoch 480
marked osd lost in epoch 482
marked osd lost in epoch 487
marked osd lost in epoch 483
marked osd lost in epoch 489
marked osd lost in epoch 485
--- * ---
2) Remove OSDs from CRUSH map
# for o in 6 13 15 19 23 27;do ceph osd crush remove osd.$o; ceph
osd down $o; ceph osd rm $o; ceph auth del osd.$o; done
removed item id 6 name 'osd.6' from crush map
osd.6 is already down.
removed osd.6
updated
removed item id 13 name 'osd.13' from crush map
osd.13 is already down.
removed osd.13
updated
removed item id 15 name 'osd.15' from crush map
osd.15 is already down.
removed osd.15
updated
removed item id 19 name 'osd.19' from crush map
osd.19 is already down.
removed osd.19
updated
removed item id 23 name 'osd.23' from crush map
osd.23 is already down.
removed osd.23
updated
removed item id 27 name 'osd.27' from crush map
osd.27 is already down.
removed osd.27
updated
--- * ---
3) Give time to the cluster react, and to the recover I/O to finish.
--- * ---
4) Check which PGS are still stale
# ceph pg dump_stuck stale
ok
pg_stat state up up_primary acting acting_primary
1.23 stale+undersized+degraded+peered [23] 23 [23] 23
2.38b stale+undersized+degraded+peered [23] 23 [23] 23
(...)
--- * ---
5) Try to query those stale PGs
# for pg in `ceph pg dump_stuck stale | grep ^[12] | awk '{print
$1}'`; do ceph pg $pg query; done
ok
Error ENOENT: i don't have pgid 1.23
Error ENOENT: i don't have pgid 2.38b
(...)
--- * ---
6) Create the non existing PGs
# for pg in `ceph pg dump_stuck stale | grep ^[12] | awk '{print
$1}'`; do ceph pg force_create_pg $pg; done
ok
pg 1.23 now creating, ok
pg 2.38b now creating, ok
(...)
--- * ---
7) At this point, for the PGs to leave the 'creating' status, I
had to restart all remaining OSDs. Otherwise those PGs were in the
creating state forever.
--
Goncalo Borges
Research Computing
ARC Centre of Excellence for Particle Physics at the Terascale
School of Physics A28 | University of Sydney, NSW 2006
T:+61 2 93511937 <tel:%2B61%202%2093511937>
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--
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Blog:
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