Then you were clearly paying more attention than me. ;-) We had some
maintenance going on during that talk, so I couldn't really focus
entirely on listening. But thanks for clarifying!
Zitat von Frédéric Nass <frederic.nass@xxxxxxxxxxxxxxxx>:
Hi Eugen,
During the talk you've mentioned, Dan said there's a hard coded
limit of 256 MDSs per cluster. So with one active and one
standby-ish MDSs per filesystem, that would be 128 filesystems at
max per cluster.
Mark said he got 120 but.. things start to get wacky by 80. :-)
More fun to come, for sure.
Cheers,
Frédéric.
[1] https://youtu.be/qiCE1Ifws80?t=2602
----- Le 21 Nov 24, à 9:36, Eugen Block eblock@xxxxxx a écrit :
I'm not aware of any hard limit for the number of Filesystems, but
that doesn't really mean very much. IIRC, last week during a Clyso
talk at Eventbrite I heard someone say that they deployed around 200
Filesystems or so, I don't remember if it was a production environment
or just a lab environment. I assume that you would probably be limited
by the number of OSDs/PGs rather than by the number of Filesystems,
200 Filesystems require at least 400 pools. But maybe someone else has
more experience in scaling CephFS that way. What we did was to scale
the number of active MDS daemons for one CephFS. I believe in the end
the customer had 48 MDS daemons on three MDS servers, 16 of them were
active with directory pinning, at that time they had 16 standby-replay
and 16 standby daemons. But it turned out that standby-replay didn't
help their use case, so we disabled standby-replay.
Can you show the entire 'ceph fs status' output? Any maybe also 'ceph
fs dump'?
Zitat von Александр Руденко <a.rudikk@xxxxxxxxx>:
Just for testing purposes, have you tried pinning rank 1 to some other
directory? Does it still break the CephFS if you stop it?
Yes, nothing changed.
It's no problem that FS hangs when one of the ranks goes down, we will have
standby-reply for all ranks. I don't like that rank which is not pinned to
some dir handled some io of this dir or from clients which work with this
dir.
I mean that I can't robustly and fully separate client IO by ranks.
Would it be an option to rather use multiple Filesystems instead of
multi-active for one CephFS?
Yes, it's an option. But it is much more complicated in our case. Btw, do
you know how many different FS can be created in one cluster? Maybe you
know some potential problems with 100-200 FSs in one cluster?
ср, 20 нояб. 2024 г. в 17:50, Eugen Block <eblock@xxxxxx>:
Ah, I misunderstood, I thought you wanted an even distribution across
both ranks.
Just for testing purposes, have you tried pinning rank 1 to some other
directory? Does it still break the CephFS if you stop it? I'm not sure
if you can prevent rank 1 from participating, I haven't looked into
all the configs in quite a while. Would it be an option to rather use
multiple Filesystems instead of multi-active for one CephFS?
Zitat von Александр Руденко <a.rudikk@xxxxxxxxx>:
> No it's not a typo. It's misleading example)
>
> dir1 and dir2 are pinned to rank 0, but FS and dir1,dir2 can't work
without
> rank 1.
> rank 1 is used for something when I work with this dirs.
>
> ceph 16.2.13, metadata balancer and policy based balancing not used.
>
> ср, 20 нояб. 2024 г. в 16:33, Eugen Block <eblock@xxxxxx>:
>
>> Hi,
>>
>> > After pinning:
>> > setfattr -n ceph.dir.pin -v 0 /fs-mountpoint/dir1
>> > setfattr -n ceph.dir.pin -v 0 /fs-mountpoint/dir2
>>
>> is this a typo? If not, you did pin both directories to the same rank.
>>
>> Zitat von Александр Руденко <a.rudikk@xxxxxxxxx>:
>>
>> > Hi,
>> >
>> > I try to distribute all top level dirs in CephFS by different MDS
ranks.
>> > I have two active MDS with rank *0* and *1 *and I have 2 top
dirs like
>> > */dir1* and* /dir2*.
>> >
>> > After pinning:
>> > setfattr -n ceph.dir.pin -v 0 /fs-mountpoint/dir1
>> > setfattr -n ceph.dir.pin -v 0 /fs-mountpoint/dir2
>> >
>> > I can see next INOS and DNS distribution:
>> > RANK STATE MDS ACTIVITY DNS INOS DIRS CAPS
>> > 0 active c Reqs: 127 /s 12.6k 12.5k 333 505
>> > 1 active b Reqs: 11 /s 21 24 19 1
>> >
>> > When I write to dir1 I can see a small amount on Reqs: in rank 1.
>> >
>> > Events in journal of MDS with rank 1:
>> > cephfs-journal-tool --rank=fs1:1 event get list
>> >
>> > 2024-11-20T12:24:42.045056+0300 0xc5c1cb UPDATE:
(scatter_writebehind)
>> > A2037D53
>> > 2024-11-20T12:24:46.935934+0300 0xc5c629 SESSION: ()
>> > 2024-11-20T12:24:47.192012+0300 0xc5c7cd UPDATE: (lock inest
accounted
>> > scatter stat update)
>> > 2024-11-20T12:24:47.904717+0300 0xc5ca0b SESSION: ()
>> > 2024-11-20T12:26:46.912719+0300 0xc5ca98 SESSION: ()
>> > 2024-11-20T12:26:47.910806+0300 0xc5cc3c SESSION: ()
>> > 2024-11-20T12:27:35.746239+0300 0xc5ccc9 SESSION: ()
>> > 2024-11-20T12:28:46.923812+0300 0xc5ce63 SESSION: ()
>> > 2024-11-20T12:28:47.903066+0300 0xc5d007 SESSION: ()
>> > 2024-11-20T12:29:08.063326+0300 0xc5d094 EXPORT: ()
>> > di1/A2037D53
>> > 2024-11-20T12:30:46.909621+0300 0xc5d96f SESSION: ()
>> > 2024-11-20T12:30:47.908050+0300 0xc5db13 SESSION: ()
>> > 2024-11-20T12:32:46.907649+0300 0xc5dba0 SESSION: ()
>> > 2024-11-20T12:32:47.905962+0300 0xc5dd44 SESSION: ()
>> > 2024-11-20T12:34:44.349348+0300 0xc5ddd1 SESSIONS: ()
>> >
>> > But the main problem, when I stop MDS rank 1 (without any kind of
>> standby)
>> > - FS hangs for all actions.
>> > Is this correct? Is it possible to completely exclude rank 1 from
>> > processing dir1 and not stop io when rank 1 goes down?
>> > _______________________________________________
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>>
>>
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