Re: Slow ops during index pool recovery causes cluster performance drop to 1%

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Hi Istvan, 

Changing the scheduler to 'wpq' could help you to quickly identify if the issue you're facing is related to 'mclock' or not. 

If you stick with mclock, depending on the rotational status of each OSD (ceph osd metadata N | jq -r .rotational), you should set each OSD's spec (osd_mclock_max_capacity_iops_hdd if rotational=1 or osd_mclock_max_capacity_iops_ssd if rotational=0) to the value you calculated, instead of letting the OSD trying to figure out and set a value that may not be accurate, especially with multiple OSDs sharing the same underlying device. 

Have you tried setting each OSD's max capacity (ceph config set osd.N osd_mclock_max_capacity_iops_[hdd, ssd])? 

Also, make sure the rotational status reported for each OSDs by ceph osd metadata osd.N actually matches the underlying hardware type. This is not always the case depending on how the disks are connected. 
If it's not, you might have to force it on boot with a udev rule. 

Regards, 
Frédéric. 

----- Le 13 Nov 24, à 9:43, Istvan Szabo, Agoda <Istvan.Szabo@xxxxxxxxx> a écrit : 

> Hi Frédéric,

> Thank you the ideas.

> Cluster is half updated but on the osds which updated are:

> "osd_op_queue": "mclock_scheduler",
> "osd_op_queue_cut_off": "high",

> I'd say the value when I do the benchmark how ceph calculates it, it is too
> high. We have 4 osd on 1 nvme and it sets the value on the last osd from the 4
> on nvme which is the highest:
> 36490.280637

> However I changed this value already on some other fully upgraded cluster
> divided by 4 and didn't help.
> Buffered io turned on since octopus, didn't change it.

> For a quick check that specific osd seems like what you tell:

> 1 : device size 0x6fc7c00000 : own
> 0x[40000~4e00000,12f70000~2252d0000,23b060000~21a230000,4583e0000~20f890000,6b1630000~200000000,35a78f0000~478a20000]
> = 0xccc5b0000 : using 0xa60ed0000(42 GiB) : bluestore has 0x62e79f0000(396 GiB)
> available
> wal_total:0, db_total:456087987814, slow_total:0

> Istvan

> From: Frédéric Nass <frederic.nass@xxxxxxxxxxxxxxxx>
> Sent: Monday, November 4, 2024 4:14 PM
> To: Szabo, Istvan (Agoda) <Istvan.Szabo@xxxxxxxxx>
> Cc: Tyler Stachecki <stachecki.tyler@xxxxxxxxx>; Ceph Users <ceph-users@xxxxxxx>
> Subject: Re:  Re: Slow ops during index pool recovery causes cluster
> performance drop to 1%
> Email received from the internet. If in doubt, don't click any link nor open any
> attachment !
> ________________________________

> Hi Istvan,

> Is you upgraded cluster using wpq or mclock scheduler? (ceph tell osd.X config
> show | grep osd_op_queue)

> Maybe your OSDs set their osd_mclock_max_capacity_iops_* capacity too low on
> start (ceph config dump | grep osd_mclock_max_capacity_iops) limiting their
> performance.

> You might want to raise these figures if set or go back to wpq to give you
> enough time to understand how mclock works.

> Also, check bluefs_buffered_io as it's default value changed over time. Better
> run 'true' now (ceph tell osd.X config show | grep bluefs_buffered_io)
> Also, check for any overspilling as there's been a bug in the past with
> overspilling not being reported on ceph status (ceph tell osd.X bluefs stats,
> SLOW line should show 0 Bytes and 0 FILES).

> Regards,
> Frédéric.

> ----- Le 4 Nov 24, à 5:24, Istvan Szabo, Agoda Istvan.Szabo@xxxxxxxxx a écrit :

> > Hi Tyler,

> > To be honest we don't have anything set by ourselves regarding compaction and
> > rocksdb:
> > When I check the socket with ceph daemon on nvme and on ssd both have default
> > false on compactL
> > "mon_compact_on_start": "false"
> > "osd_compact_on_start": "false",

> > Rocksdb also default:
> > bluestore_rocksdb_options":
> > "compression=kNoCompression,max_write_buffer_number=4,min_write_buffer_number_to_merge=1,recycle_log_file_num=4,write_buffer_size=268435456,writable_file_max_buffer_size=0,compaction_readahead_size=2097152,max_background_compactions=2,max_total_wal_size=1073741824"

> > This is 1 event during the slow ops out of the 20:
>> [
>> https://gist.githubusercontent.com/Badb0yBadb0y/30de736f5d2bd6ec48aa7acf0a3caa14/raw/1070acbf82cc8d69efc04e4e0583e7f83bd33b3f/gistfile1.txt
> > |
> https://gist.githubusercontent.com/Badb0yBadb0y/30de736f5d2bd6ec48aa7acf0a3caa14/raw/1070acbf82cc8d69efc04e4e0583e7f83bd33b3f/gistfile1.txt
> ]

> > All belongs to a bucket which doing streaming operation which means continuous
> > delete and upload 24/7.

> > I can see throttled options but still don't understand why the high latency.


> > ty

> > ________________________________
> > From: Tyler Stachecki <stachecki.tyler@xxxxxxxxx>
> > Sent: Sunday, November 3, 2024 4:07 PM
> > To: Szabo, Istvan (Agoda) <Istvan.Szabo@xxxxxxxxx>
> > Cc: Ceph Users <ceph-users@xxxxxxx>
> > Subject: Re:  Re: Slow ops during index pool recovery causes cluster
> > performance drop to 1%

> > Email received from the internet. If in doubt, don't click any link nor open any
> > attachment !
> > ________________________________

> > On Sun, Nov 3, 2024 at 1:28 AM Szabo, Istvan (Agoda)
> > <Istvan.Szabo@xxxxxxxxx> wrote:
> >> Hi,

> >> I'm updating from octopus to quincy and all in our cluster when index pool
> >> recovery kicks off, cluster operation drops to 1%, slow ops comes non-stop.
> >> The recovery takes 1-2 hours/nodes.

> >> What I can see the iowait on the nvme drives which belongs to the index pool is
> >> pretty high, however the throughput is less than 500MB/s, the iops is less than
> >> 5000/sec.
> > ...
> >> after update and machine reboot compaction kicks off which generates 30-40
> >> iowait on the node, we prevent with "noup" flag to put these osds into the
> >> cluster until compaction finished, however when we have 0 iowait after
> >> compaction, I unset noup so recovery can start which causes the above issue. If
> >> I wouldn't set noup it would cause even bigger issue.

> > By any chance, are you specifying a value for
> > bluestore_rocksdb_options in your ceph.conf? The compaction
> > observation at reboot in particular is odd.

> > Tyler

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> This message is confidential and is for the sole use of the intended
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> message. All messages sent to and from Agoda may be monitored to ensure
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> remove potential malware. Electronic messages may be intercepted, amended, lost
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