From technical/developer's point of view I don't see any issues with
tuning this option. But since now I wouldn't recommend to enable it in
production as it partially bypassed our regular development cycle. Being
enabled in master for a while by default allows more develpers to
use/try the feature before release. This can be considered as an
additional implicit QA process. But as we just discovered this hasn't
happened.
Hence you can definitely try it but this exposes your cluster(s) to some
risk as for any new (and incompletely tested) feature....
Thanks,
Igor
On 8/20/2020 4:06 PM, Seena Fallah wrote:
Greate, thanks.
Is it safe to change it manually in ceph.conf until next nautilus
release or should I wait for the next nautilus release for this
change? I mean does qa run on this value for this config that we could
trust and change it or should we wait until the next nautilus release
that qa ran on this value?
On Thu, Aug 20, 2020 at 5:25 PM Igor Fedotov <ifedotov@xxxxxxx
<mailto:ifedotov@xxxxxxx>> wrote:
Hi Seena,
this parameter isn't intended to be adjusted in production
environments - it's supposed that default behavior covers all
regular customers' needs.
The issue though is that default setting is invalid. It should be
'use_some_extra'. Gonna fix that shortly...
Thanks,
Igor
On 8/20/2020 1:44 PM, Seena Fallah wrote:
Hi Igor.
Could you please tell why this config is in LEVEL_DEV
(https://github.com/ceph/ceph/pull/29687/files#diff-3d7a065928b2852c228ffe669d7633bbR4587)?
As it is documented in Ceph we can't use LEVEL_DEV in production
environments!
Thanks
On Thu, Aug 20, 2020 at 1:58 PM Igor Fedotov <ifedotov@xxxxxxx
<mailto:ifedotov@xxxxxxx>> wrote:
Hi Simon,
starting Nautlus v14.2.10 Bluestore is able to use 'wasted'
space at DB
volume.
see this PR: https://github.com/ceph/ceph/pull/29687
Nice overview on the overall BlueFS/RocksDB design can be
find here:
https://cf2.cloudferro.com:8080/swift/v1/AUTH_5e376cddf8a94f9294259b5f48d7b2cd/ceph/rocksdb_in_ceph.pdf
Which also includes some overview (as well as additional
concerns) for
changes brought by the above-mentioned PR.
Thanks,
Igor
On 8/20/2020 11:39 AM, Simon Oosthoek wrote:
> Hi Michael,
>
> thanks for the explanation! So if I understand correctly,
we waste 93
> GB per OSD on unused NVME space, because only 30GB is
actually used...?
>
> And to improve the space for rocksdb, we need to plan for
300GB per
> rocksdb partition in order to benefit from this advantage....
>
> Reducing the number of small files is something we always
ask of our
> users, but reality is what it is ;-)
>
> I'll have to look into how I can get an informative view on
these
> metrics... It's pretty overwhelming the amount of
information coming
> out of the ceph cluster, even when you look only
superficially...
>
> Cheers,
>
> /Simon
>
> On 20/08/2020 10:16, Michael Bisig wrote:
>> Hi Simon
>>
>> As far as I know, RocksDB only uses "leveled" space on the
NVME
>> partition. The values are set to be 300MB, 3GB, 30GB and
300GB. Every
>> DB space above such a limit will automatically end up on
slow devices.
>> In your setup where you have 123GB per OSD that means you
only use
>> 30GB of fast device. The DB which spills over this limit
will be
>> offloaded to the HDD and accordingly, it slows down
requests and
>> compactions.
>>
>> You can proof what your OSD currently consumes with:
>> ceph daemon osd.X perf dump
>>
>> Informative values are `db_total_bytes`, `db_used_bytes` and
>> `slow_used_bytes`. This changes regularly because of the
ongoing
>> compactions but Prometheus mgr module exports these values
such that
>> you can track it.
>>
>> Small files generally leads to bigger RocksDB, especially
when you
>> use EC, but this depends on the actual amount and file sizes.
>>
>> I hope this helps.
>> Regards,
>> Michael
>>
>> On 20.08.20, 09:10, "Simon Oosthoek"
<s.oosthoek@xxxxxxxxxxxxx <mailto:s.oosthoek@xxxxxxxxxxxxx>>
wrote:
>>
>> Hi
>>
>> Recently our ceph cluster (nautilus) is experiencing
bluefs
>> spillovers,
>> just 2 osd's and I disabled the warning for these osds.
>> (ceph config set osd.125
bluestore_warn_on_bluefs_spillover false)
>>
>> I'm wondering what causes this and how this can be
prevented.
>>
>> As I understand it the rocksdb for the OSD needs to
store more
>> than fits
>> on the NVME logical volume (123G for 12T OSD). A way
to fix it
>> could be
>> to increase the logical volume on the nvme (if there
was space
>> on the
>> nvme, which there isn't at the moment).
>>
>> This is the current size of the cluster and how much
is free:
>>
>> [root@cephmon1 ~]# ceph df
>> RAW STORAGE:
>> CLASS SIZE AVAIL USED RAW USED
>> %RAW USED
>> hdd 1.8 PiB 842 TiB 974 TiB 974
>> TiB 53.63
>> TOTAL 1.8 PiB 842 TiB 974 TiB 974
>> TiB 53.63
>>
>> POOLS:
>> POOL ID STORED OBJECTS USED
>> %USED MAX AVAIL
>> cephfs_data 1 572 MiB
121.26M 2.4 GiB
>> 0 167 TiB
>> cephfs_metadata 2 56 GiB
5.15M 57 GiB
>> 0 167 TiB
>> cephfs_data_3copy 8 201 GiB
51.68k 602 GiB
>> 0.09 222 TiB
>> cephfs_data_ec83 13 643 TiB
279.75M 953 TiB
>> 58.86 485 TiB
>> rbd 14 21 GiB
5.66k 64 GiB
>> 0 222 TiB
>> .rgw.root 15 1.2 KiB 4 1 MiB
>> 0 167 TiB
>> default.rgw.control 16 0 B 8 0 B
>> 0 167 TiB
>> default.rgw.meta 17 765 B 4 1 MiB
>> 0 167 TiB
>> default.rgw.log 18 0 B 207 0 B
>> 0 167 TiB
>> cephfs_data_ec57 20 433 MiB
230 1.2 GiB
>> 0 278 TiB
>>
>> The amount used can still grow a bit before we need
to add
>> nodes, but
>> apparently we are running into the limits of our rocskdb
>> partitions.
>>
>> Did we choose a parameter (e.g. minimal object size)
too small,
>> so we
>> have too much objects on these spillover OSDs? Or is
it that too
>> many
>> small files are stored on the cephfs filesystems?
>>
>> When we expand the cluster, we can choose larger nvme
devices to
>> allow
>> larger rocksdb partitions, but is that the right way
to deal
>> with this,
>> or should we adjust some parameters on the cluster
that will
>> reduce the
>> rocksdb size?
>>
>> Cheers
>>
>> /Simon
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