ceph df (octopus) 显示在纠删码池中，USED 比 STORED 高 7 倍

问题描述

池 default.rgw.buckets.data 已存储 501 GiB，但 USED 显示 3.5 TiB。

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

default.rgw.buckets.data 池正在使用纠删码：

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

如果有人能帮助解释为什么它使用了 7 倍以上的空间，那将大有帮助。 版本控制被禁用。 ceph 版本 15.2.13（章鱼稳定版）。

解决方法

这与 bluestore_min_alloc_size_hdd=64K（八达通的默认值）有关。我将升级到 Pacific 并更改为 bluestore_min_alloc_size_hdd=4K 这应该会有所帮助。

Josh Baergen 在邮件列表中回复：

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