That's bluefs buffered io = false which did the trick.
It modified write path and this presumably has fixed large write(s).
Trying to reproduce locally but please preserve at least one failing OSD
(i.e. do not start it with the disabled buffered io) for future
experiments/troubleshooting for a while if possible.
Thanks,
Igor
On 4/29/2020 4:50 PM, Francois Legrand wrote:
Hi,
It seems much better with theses options. The osd is now up since 10mn
without crashing (before it was rebooting after ~1mn).
F.
Le 29/04/2020 à 15:16, Igor Fedotov a écrit :
Hi Francois,
I'll write a more thorough response a bit later.
Meanwhile could you please try OSD startup with the following
settings now:
debug-bluefs abd debug-bdev = 20
bluefs sync write = false
bluefs buffered io = false
Thanks,
Igor
On 4/29/2020 3:35 PM, Francois Legrand wrote:
Hi Igor,
Here is what we did :
First, as other osd were falling down, we stopped all operations with
ceph osd set norecover
ceph osd set norebalance
ceph osd set nobackfill
ceph osd set pause
to avoid other crashs !
Then we moved to your recommandations (still testing on osd 5):
in /etc/ceph/ceph.conf we added:
[osd.5]
debug bluefs = 20
debug bdev = 20
We ran :
ceph-bluestore-tool fsck --path /var/lib/ceph/osd/ceph-5 -l
/var/log/ceph/bluestore-tool-fsck-osd-5.log --log-level 20 >
/var/log/ceph/bluestore-tool-fsck-osd-5.out 2>&1
it ended with fsck success
It seems that the default value for bluefs sync write is false
(https://github.com/ceph/ceph/blob/v14.2.8/src/common/options.cc), thus
we changed /etc/ceph/ceph.conf to :
[osd.5]
debug bluefs = 20
debug bdev = 20
bluefs sync write = true
and restarted the osd. It crashed !
We tryed to change explicitely bluefs sync write = false and
restarted... same result !
The logs are here : https://we.tl/t-HMiFDu22XH
Moreover, we have a rados gateway pool with hundreds of 4GB files.
Can this be the origin of the problem ?
Do you thing that removing this pool can help ?
Thanks again for your expertise.
F.
Le 28/04/2020 à 18:52, Igor Fedotov a écrit :
Short update - please treat bluefs_sync_write parameter instead of
bdev-aio. Changing the latter isn't supported in fact.
On 4/28/2020 7:35 PM, Igor Fedotov wrote:
Francious,
here are some observations got from your log.
1) Rocksdb reports error on the following .sst file:
-35> 2020-04-28 15:23:47.612 7f4856e82a80 -1 rocksdb:
Corruption: Bad table magic number: expected 986351839
0377041911, found 12950032858166034944 in db/068269.sst
2) which relates to BlueFS ino 53361:
-50> 2020-04-28 15:23:45.103 7f4856e82a80 10 bluefs
open_for_read db/068269.sst (random)
-49> 2020-04-28 15:23:45.103 7f4856e82a80 10 bluefs
open_for_read h 0x557914fb80b0 on file(ino 53361 size 0x
c496f919 mtime 2020-04-28 15:23:39.827515 bdev 1 allocated
c4970000 extents [1:0x383db280000~c4970000])
3) and failed read happens to the end (0xc496f8e4~35, last 0x35
bytes) of this huge(3+GB) file:
-44> 2020-04-28 15:23:47.514 7f4856e82a80 10 bluefs _read_random
h 0x557914fb80b0 0xc496f8e4~35 from file(in
o 53361 size 0xc496f919 mtime 2020-04-28 15:23:39.827515 bdev 1
allocated c4970000 extents [1:0x383db280000~c49
70000])
-43> 2020-04-28 15:23:47.514 7f4856e82a80 20 bluefs
_read_random left 0x71c 0xc496f8e4~35
-42> 2020-04-28 15:23:47.514 7f4856e82a80 20 bluefs
_read_random got 53
4) This .sst file was created from scratch shortly before with a
single-shot 3+GB write:
-88> 2020-04-28 15:23:35.661 7f4856e82a80 10 bluefs
open_for_write db/068269.sst
-87> 2020-04-28 15:23:35.661 7f4856e82a80 20 bluefs
open_for_write mapping db/068269.sst to bdev 1
-86> 2020-04-28 15:23:35.662 7f4856e82a80 10 bluefs
open_for_write h 0x5579145e7a40 on file(ino 53361 size 0
x0 mtime 2020-04-28 15:23:35.663142 bdev 1 allocated 0 extents [])
-85> 2020-04-28 15:23:39.826 7f4856e82a80 10 bluefs _flush
0x5579145e7a40 0x0~c496f919 to file(ino 53361 siz
e 0x0 mtime 2020-04-28 15:23:35.663142 bdev 1 allocated 0 extents [])
5) Presumably RocksDB creates this file in an attempt to
recover/compact/process another existing file (ino 52405) which
is pretty large as well
Please find multiple earlier reads, the last one:
-92> 2020-04-28 15:23:29.857 7f4856e82a80 10 bluefs _read h
0x5579147286e0 0xc6788000~8000 from file(ino 524
05 size 0xc67888a0 mtime 2020-04-25 13:34:55.325699 bdev 0
allocated c6790000 extents [1:0x381c8220000~10000,1:
The rationales for binding these two files are pretty uncommon
file sizes.
So you have 3+GB single-shot BlueFS write and immediate read from
the end of the written extent which returns unexpected magic.
It's well known in the software world that large (2+GB) data
processing implementations tend to be error-prone. And Ceph is not
an exception. Here is a couple of recent examples which are pretty
close to your case:
https://github.com/ceph/ceph/commit/4d33114a40d5ae0d541c36175977ca22789a3b88
https://github.com/ceph/ceph/commit/207806abaa91259d9bb726c2555e7e21ac541527
Although they are already fixed in Nautilus 14.2.8 there might be
others present along the write path (including H/W firmware).
The good news are that failure happens on a newly written file
(remember invalid magic is read at the end(!) of this new large
file shortly(!) after the write). So looks like data hasn't yet
landed to a disk. And hopefully original data are untouched.
You can try to run ceph-bluestore-tool's fsck command on the
broken OSD. This will open DB in read-only and hopefully proves
the idea that the issue is on the write path rather than already
corrupted data.
Also you might want to set bdev-aio to false (or true if it's
already at false) and try OSD startup once more - this will go via
a bit different write path and may be provide a workaround.
Also please collect debug logs for OSD startup (with both current
and updated bdev-aio parameter) and --debug-bdev/debug-bluefs set
to 20. You can omit --debug-bluestore increase for now to reduce
log size.
Thanks,
Igor
On 4/28/2020 5:16 PM, Francois Legrand wrote:
Here is the output of ceph-bluestore-tool bluefs-bdev-sizes
inferring bluefs devices from bluestore path
slot 1 /var/lib/ceph/osd/ceph-5/block -> /dev/dm-17
1 : device size 0x746c0000000 : own 0x[37e1eb00000~4a82900000] =
0x4a82900000 : using 0x5bc780000(23 GiB)
the result of the debug-bluestore (and debug-bluefs) set to 20
for osd.5
is at the following address (28MB).
https://wetransfer.com/downloads/a193ab15ab5e2395fe2462c963507a7f20200428141355/5da2ebf0d33750a5fde85bf662cf0e6d20200428141415/55849f?utm_campaign=WT_email_tracking&utm_content=general&utm_medium=download_button&utm_source=notify_recipient_email
Thanks for your help.
F.
Le 28/04/2020 à 13:33, Igor Fedotov a écrit :
Hi Francois,
Could you please share OSD startup log with debug-bluestore (and
debug-bluefs) set to 20.
Also please run ceph-bluestore-tool's bluefs-bdev-sizes command
and share the output.
Thanks,
Igor
On 4/28/2020 12:55 AM, Francois Legrand wrote:
Hi all,
*** Short version ***
Is there a way to repair a rocksdb from errors "Encountered
error while reading data from compression dictionary block
Corruption: block checksum mismatch" and "_open_db erroring
opening db" ?
*** Long version ***
We operate a nautilus ceph cluster (with 100 disks of 8TB in 6
servers + 4 mons/mgr + 3 mds).
We recently (Monday 20) upgraded from 14.2.7 to 14.2.8. This
triggered a rebalancing of some data.
Two days later (Wednesday 22) we had a very short power outage.
Only one of the osd servers went down (and unfortunately died).
This triggered a reconstruction of the losts osds. Operations
went fine until Saturday 25 where some osds in the 5 remaining
servers started to crash apparently with no reasons.
We tryed to restart them, but they crashed again. We ended with
18 osd down (+ 16 in the dead server so 34 osd downs out of 100).
Looking at the logs we found for all the crashed osd :
-237> 2020-04-25 16:32:51.835 7f1f45527a80 3 rocksdb:
[table/block_based_table_reader.cc:1117] Encountered error
while reading data from compression dictionary block
Corruption: block checksum mismatch: expected 0, got
2729370997 in db/181355.sst offset 18446744073709551615 size
18446744073709551615
and
2020-04-25 16:05:47.251 7fcbd1e46a80 -1
bluestore(/var/lib/ceph/osd/ceph-3) _open_db erroring opening db:
We also noticed that the "Encountered error while reading data
from compression dictionary block Corruption: block checksum
mismatch" was present few days before the crash.
We also have some osd with this error but still up.
We tryed to repair with :
ceph-kvstore-tool bluestore-kv /var/lib/ceph/osd/ceph-3 repair
But no success (it ends with _open_db erroring opening db).
Thus does somebody have an idea to fix this or at least know if
it's possible to repair and correct the "Encountered error
while reading data from compression dictionary block
Corruption: block checksum mismatch" and "_open_db erroring
opening db" !
Thanks for your help (we are desperate because we will loose
datas and are fighting to save something) !!!
F.
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