PG subfolder splitting is the primary reason people are
going to be deploying Luminous and Bluestore much faster
than any other major release of Ceph. Bluestore removes the
concept of subfolders in PGs.
I have had clusters that reached what seemed a hardcoded
maximum of 12,800 objects in a subfolder. It would take an
osd_heartbeat_grace of 240 or 300 to let them finish
splitting their subfolders without being marked down.
Recently I came across a cluster that had a setting of 240
objects per subfolder before splitting, so it was splitting
all the time, and several of the OSDs took longer than 30
seconds to finish splitting into subfolders. That led to
more problems as we started adding backfilling to everything
and we lost a significant amount of throughput on the cluster.
I have yet to manage a cluster with a recent enough version
of the ceph-objectstore-tool (hopefully I'll have one this
month) that includes the ability to take an osd offline,
split the subfolders, then bring it back online. If you set
up a way to monitor how big your subfolders are getting, you
can leave the ceph settings as high as you want, and then go
in and perform maintenance on your cluster 1 failure domain
at a time splitting all of the PG subfolders on the OSDs.
This approach would remove this ever happening in the wild.
On Wed, May 10, 2017 at 5:37 AM Piotr Nowosielski
<piotr.nowosiel...@allegrogroup.com
<mailto:piotr.nowosiel...@allegrogroup.com>> wrote:
It is difficult for me to clearly state why some PGs
have not been migrated.
crushmap settings? Weight of OSD?
One thing is certain - you will not find any information
about the split
process in the logs ...
pn
-----Original Message-----
From: Anton Dmitriev [mailto:t...@enumnet.ru
<mailto:t...@enumnet.ru>]
Sent: Wednesday, May 10, 2017 10:14 AM
To: Piotr Nowosielski
<piotr.nowosiel...@allegrogroup.com
<mailto:piotr.nowosiel...@allegrogroup.com>>;
ceph-users@lists.ceph.com <mailto:ceph-users@lists.ceph.com>
Subject: Re: [ceph-users] All OSD fails after few
requests to RGW
When I created cluster, I made a mistake in
configuration, and set split
parameter to 32 and merge to 40, so 32*40*16 = 20480
files per folder.
After that I changed split to 8, and increased number of
pg and pgp from
2048 to 4096 for pool, where problem occurs. While it
was backfilling I
observed, that placement groups were backfilling from
one set of 3 OSD to
another set of 3 OSD (replicated size = 3), so I made a
conclusion, that PGs
are completely recreating while increasing PG and PGP
for pool and after
this process number of files per directory must be Ok.
But when backfilling
finished I found many directories in this pool with ~20
000 files. Why Increasing PG num did not helped? Or
maybe after this process
some files will be deleted with some delay?
I couldn`t find any information about directory split
process in logs, also
with osd and filestore debug 20. What pattern and in
what log I need to grep
for finding it?
On 10.05.2017 10:36, Piotr Nowosielski wrote:
> You can:
> - change these parameters and use ceph-objectstore-tool
> - add OSD host - rebuild the cluster will reduce the
number of files
> in the directories
> - wait until "split" operations are over ;-)
>
> In our case, we could afford to wait until the "split"
operation is
> over (we have 2 clusters in slightly different
configurations storing
> the same data)
>
> hint:
> When creating a new pool, use the parameter
"expected_num_objects"
>
https://www.suse.com/documentation/ses-4/book_storage_admin/data/ceph_
> pools_operate.html
>
> Piotr Nowosielski
> Senior Systems Engineer
> Zespół Infrastruktury 5
> Grupa Allegro sp. z o.o.
> Tel: +48 512 08 55 92
>
>
> -----Original Message-----
> From: Anton Dmitriev [mailto:t...@enumnet.ru
<mailto:t...@enumnet.ru>]
> Sent: Wednesday, May 10, 2017 9:19 AM
> To: Piotr Nowosielski
<piotr.nowosiel...@allegrogroup.com
<mailto:piotr.nowosiel...@allegrogroup.com>>;
> ceph-users@lists.ceph.com
<mailto:ceph-users@lists.ceph.com>
> Subject: Re: [ceph-users] All OSD fails after few
requests to RGW
>
> How did you solved it? Set new split/merge thresholds,
and manually
> applied it by ceph-objectstore-tool --data-path
> /var/lib/ceph/osd/ceph-${osd_num} --journal-path
> /var/lib/ceph/osd/ceph-${osd_num}/journal
>
--log-file=/var/log/ceph/objectstore_tool.${osd_num}.log
--op
> apply-layout-settings --pool default.rgw.buckets.data
>
> on each OSD?
>
> How I can see in logs, that split occurs?
>
> On 10.05.2017 10:13, Piotr Nowosielski wrote:
>> Hey,
>> We had similar problems. Look for information on
"Filestore merge and
>> split".
>>
>> Some explain:
>> The OSD, after reaching a certain number of files in
the directory
>> (it depends of 'filestore merge threshold' and
'filestore split multiple'
>> parameters) rebuilds the structure of this directory.
>> If the files arrives, the OSD creates new
subdirectories and moves
>> some of the files there.
>> If the files are missing the OSD will reduce the
number of
>> subdirectories.
>>
>>
>> --
>> Piotr Nowosielski
>> Senior Systems Engineer
>> Zespół Infrastruktury 5
>> Grupa Allegro sp. z o.o.
>> Tel: +48 512 08 55 92
>>
>> Grupa Allegro Sp. z o.o. z siedzibą w Poznaniu,
60-166 Poznań, przy ul.
>> Grunwaldzka 182, wpisana do rejestru przedsiębiorców
prowadzonego
>> przez Sąd Rejonowy Poznań - Nowe Miasto i Wilda,
Wydział VIII
>> Gospodarczy Krajowego Rejestru Sądowego pod numerem
KRS 0000268796, o
>> kapitale zakładowym w wysokości 33 976 500,00 zł,
posiadająca numer
>> identyfikacji podatkowej NIP: 5272525995.
>>
>>
>>
>> -----Original Message-----
>> From: ceph-users
[mailto:ceph-users-boun...@lists.ceph.com
<mailto:ceph-users-boun...@lists.ceph.com>] On Behalf
>> Of Anton Dmitriev
>> Sent: Wednesday, May 10, 2017 8:14 AM
>> To: ceph-users@lists.ceph.com
<mailto:ceph-users@lists.ceph.com>
>> Subject: Re: [ceph-users] All OSD fails after few
requests to RGW
>>
>> Hi!
>>
>> I increased pg_num and pgp_num for pool
default.rgw.buckets.data from
>> 2048 to 4096, and it seems that situation became a
bit better,
>> cluster dies after 20-30 PUTs, not after 1. Could
someone please give
>> me some recommendations how to rescue the cluster?
>>
>> On 27.04.2017 09:59, Anton Dmitriev wrote:
>>> Cluster was going well for a long time, but on the
previous week
>>> osds start to fail.
>>> We use cluster like image storage for Opennebula
with small load and
>>> like object storage with high load.
>>> Sometimes disks of some osds utlized by 100 %,
iostat shows avgqu-sz
>>> over 1000, while reading or writing a few kilobytes
in a second,
>>> osds on this disks become unresponsive and cluster
marks them down.
>>> We lower the load to object storage and situation
became better.
>>>
>>> Yesterday situation became worse:
>>> If RGWs are disabled and there is no requests to
object storage
>>> cluster performing well, but if enable RGWs and make
a few PUTs or
>>> GETs all not SSD osds on all storages become in the
same situation,
>>> described above.
>>> IOtop shows, that xfsaild/<disk> burns disks.
>>>
>>> trace-cmd record -e xfs\* for a 10 seconds shows 10
milion objects,
>>> as i understand it means ~360 000 objects to push
per one osd for a
>>> 10 seconds
>>> $ wc -l t.t
>>> 10256873 t.t
>>>
>>> fragmentation on one of such disks is about 3%
>>>
>>> more information about cluster:
>>>
>>> https://yadi.sk/d/Y63mXQhl3HPvwt
>>>
>>> also debug logs for osd.33 while problem occurs
>>>
>>> https://yadi.sk/d/kiqsMF9L3HPvte
>>>
>>> debug_osd = 20/20
>>> debug_filestore = 20/20
>>> debug_tp = 20/20
>>>
>>>
>>>
>>> Ubuntu 14.04
>>> $ uname -a
>>> Linux storage01 4.2.0-42-generic #49~14.04.1-Ubuntu
SMP Wed Jun 29
>>> 20:22:11 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
>>>
>>> Ceph 10.2.7
>>>
>>> 7 storages: Supermicro 28 osd 4tb 7200 JBOD +
journal raid10 4 ssd
>>> intel 3510 800gb + 2 osd SSD intel 3710 400gb for
rgw meta and index
>>> One of this storages differs only in number of osd,
it has 26 osd on
>>> 4tb, instead of 28 on others
>>>
>>> Storages connect to each other by bonded 2x10gbit
Clients connect to
>>> storages by bonded 2x1gbit
>>>
>>> in 5 storages 2 x CPU E5-2650v2 and 256 gb RAM in 2
storages 2 x
>>> CPU
>>> E5-2690v3 and 512 gb RAM
>>>
>>> 7 mons
>>> 3 rgw
>>>
>>> Help me please to rescue the cluster.
>>>
>>>
>> --
>> Dmitriev Anton
>>
>> _______________________________________________
>> ceph-users mailing list
>> ceph-users@lists.ceph.com
<mailto:ceph-users@lists.ceph.com>
>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
> --
> Dmitriev Anton
--
Dmitriev Anton
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