Ceph on a single host makes little to no sense. You're better of running something like ZFS On Tue, 6 Jul 2021 at 23:52, Wladimir Mutel <mwg@xxxxxxxxx> wrote: > I started my experimental 1-host/8-HDDs setup in 2018 with > Luminous, > and I read > https://ceph.io/community/new-luminous-erasure-coding-rbd-cephfs/ , > which had interested me in using Bluestore and rewriteable EC > pools for RBD data. > I have about 22 TiB or raw storage, and ceph df shows this : > > --- RAW STORAGE --- > CLASS SIZE AVAIL USED RAW USED %RAW USED > hdd 22 TiB 2.7 TiB 19 TiB 19 TiB 87.78 > TOTAL 22 TiB 2.7 TiB 19 TiB 19 TiB 87.78 > > --- POOLS --- > POOL ID PGS STORED OBJECTS USED %USED MAX AVAIL > jerasure21 1 256 9.0 TiB 2.32M 13 TiB 97.06 276 GiB > libvirt 2 128 1.5 TiB 413.60k 4.5 TiB 91.77 140 GiB > rbd 3 32 798 KiB 5 2.7 MiB 0 138 GiB > iso 4 32 2.3 MiB 10 8.0 MiB 0 138 GiB > device_health_metrics 5 1 31 MiB 9 94 MiB 0.02 138 GiB > > If I add USED for libvirt and jerasure21 , I get 17.5 TiB, and 2.7 > TiB is shown at RAW STORAGE/AVAIL > Sum of POOLS/MAX AVAIL is about 840 GiB, where are my other > 2.7-0.840 =~ 1.86 TiB ??? > Or in different words, where are my (RAW STORAGE/RAW > USED)-(SUM(POOLS/USED)) = 19-17.5 = 1.5 TiB ? > > As it does not seem I would get any more hosts for this setup, > I am seriously thinking of bringing down this Ceph > and setting up instead a Btrfs storing qcow2 images served over > iSCSI > which looks simpler to me for single-host situation. > > Josh Baergen wrote: > > Hey Wladimir, > > > > I actually don't know where this is referenced in the docs, if anywhere. > Googling around shows many people discovering this overhead the hard way on > ceph-users. > > > > I also don't know the rbd journaling mechanism in enough depth to > comment on whether it could be causing this issue for you. Are you seeing a > high > > allocated:stored ratio on your cluster? > > > > Josh > > > > On Sun, Jul 4, 2021 at 6:52 AM Wladimir Mutel <mwg@xxxxxxxxx <mailto: > mwg@xxxxxxxxx>> wrote: > > > > Dear Mr Baergen, > > > > thanks a lot for your very concise explanation, > > however I would like to learn more why default Bluestore alloc.size > causes such a big storage overhead, > > and where in the Ceph docs it is explained how and what to watch for > to avoid hitting this phenomenon again and again. > > I have a feeling this is what I get on my experimental Ceph setup > with simplest JErasure 2+1 data pool. > > Could it be caused by journaled RBD writes to EC data-pool ? > > > > Josh Baergen wrote: > > > Hey Arkadiy, > > > > > > If the OSDs are on HDDs and were created with the default > > > bluestore_min_alloc_size_hdd, which is still 64KiB in Octopus, > then in > > > effect data will be allocated from the pool in 640KiB chunks > (64KiB * > > > (k+m)). 5.36M objects taking up 501GiB is an average object size > of 98KiB > > > which results in a ratio of 6.53:1 allocated:stored, which is > pretty close > > > to the 7:1 observed. > > > > > > If my assumption about your configuration is correct, then the > only way to > > > fix this is to adjust bluestore_min_alloc_size_hdd and recreate > all your > > > OSDs, which will take a while... > > > > > > Josh > > > > > > On Tue, Jun 29, 2021 at 3:07 PM Arkadiy Kulev <eth@xxxxxxxxxxxx > <mailto:eth@xxxxxxxxxxxx>> wrote: > > > > > >> The pool *default.rgw.buckets.data* has *501 GiB* stored, but > USED shows > > >> *3.5 > > >> TiB *(7 times higher!)*:* > > >> > > >> root@ceph-01:~# ceph df > > >> --- RAW STORAGE --- > > >> CLASS SIZE AVAIL USED RAW USED %RAW USED > > >> hdd 196 TiB 193 TiB 3.5 TiB 3.6 TiB 1.85 > > >> TOTAL 196 TiB 193 TiB 3.5 TiB 3.6 TiB 1.85 > > >> > > >> --- POOLS --- > > >> POOL ID PGS STORED OBJECTS USED > %USED MAX > > >> AVAIL > > >> device_health_metrics 1 1 19 KiB 12 56 KiB > 0 > > >> 61 TiB > > >> .rgw.root 2 32 2.6 KiB 6 1.1 MiB > 0 > > >> 61 TiB > > >> default.rgw.log 3 32 168 KiB 210 13 MiB > 0 > > >> 61 TiB > > >> default.rgw.control 4 32 0 B 8 0 B > 0 > > >> 61 TiB > > >> default.rgw.meta 5 8 4.8 KiB 11 1.9 MiB > 0 > > >> 61 TiB > > >> default.rgw.buckets.index 6 8 1.6 GiB 211 4.7 GiB > 0 > > >> 61 TiB > > >> > > >> default.rgw.buckets.data 10 128 501 GiB 5.36M 3.5 TiB > 1.90 > > >> 110 TiB > > >> > > >> The *default.rgw.buckets.data* pool is using erasure coding: > > >> > > >> root@ceph-01:~# ceph osd erasure-code-profile get EC_RGW_HOST > > >> crush-device-class=hdd > > >> crush-failure-domain=host > > >> crush-root=default > > >> jerasure-per-chunk-alignment=false > > >> k=6 > > >> m=4 > > >> plugin=jerasure > > >> technique=reed_sol_van > > >> w=8 > > >> > > >> If anyone could help explain why it's using up 7 times more > space, it would > > >> help a lot. Versioning is disabled. ceph version 15.2.13 > (octopus stable). > > >> > > >> Sincerely, > > >> Ark. > > >> _______________________________________________ > > >> ceph-users mailing list -- ceph-users@xxxxxxx <mailto: > ceph-users@xxxxxxx> > > >> To unsubscribe send an email to ceph-users-leave@xxxxxxx > <mailto:ceph-users-leave@xxxxxxx> > > >> > > > _______________________________________________ > > > ceph-users mailing list -- ceph-users@xxxxxxx <mailto: > ceph-users@xxxxxxx> > > > To unsubscribe send an email to ceph-users-leave@xxxxxxx <mailto: > 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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