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? >>> >> > _______________________________________________ >>> >> > ceph-users mailing list -- ceph-users@xxxxxxx >>> >> > To unsubscribe send an email to ceph-users-leave@xxxxxxx >>> >> >>> >> >>> >> _______________________________________________ >>> >> ceph-users mailing list -- ceph-users@xxxxxxx >>> >> To unsubscribe send an email to ceph-users-leave@xxxxxxx >>> >> >>> >>> >>> >>> > > > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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