On 31/01/2024 20:13, Patrick Donnelly wrote:
On Tue, Jan 30, 2024 at 5:03 AM Dietmar Rieder
<dietmar.rieder@xxxxxxxxxxx> wrote:
Hello,
I have a question regarding the default pool of a cephfs.
According to the docs it is recommended to use a fast ssd replicated
pool as default pool for cephfs. I'm asking what are the space
requirements for storing the inode backtrace information?
The actual recommendation is to use a replicated pool for the default
data pool. Regular hard drives are fine for the storage device.
Hello,
Is there a rule of thumb for the space requirements of the default pool
(depending on the number of POSIX objects) ?
One of our CephFS clusters is configured with a replicated default pool,
but we find the space usage on that pool to be very high with the
(somewhat) moderate number of files:
[ceph: root@$NODE /]# ceph df
--- RAW STORAGE ---
CLASS SIZE AVAIL USED RAW USED %RAW USED
hdd 5.9 PiB 3.9 PiB 2.0 PiB 2.0 PiB 33.53
ssd 51 TiB 35 TiB 15 TiB 15 TiB 30.08
TOTAL 5.9 PiB 3.9 PiB 2.0 PiB 2.0 PiB 33.50
--- POOLS ---
POOL ID PGS STORED OBJECTS USED %USED MAX AVAIL
device_health_metrics 2 1 733 MiB 664 2.1 GiB 0 9.9 TiB
cephfs_EC_data 3 8192 1.5 PiB 515.56M 1.9 PiB 34.22 2.9 PiB
cephfs_metadata 4 128 86 GiB 10.28M 259 GiB 0.84 9.9 TiB
cephfs_default 5 512 4.2 TiB 131.17M 13 TiB 29.87 9.9 TiB
[...]
According to our statistics, there are about 132 million files and
symlinks in the filesystem which is consistent with the number of
objects for the "cephfs_default" pool.
(same for the metadata pool and the ~10 million directories)
But 4.2 TiB stored (~32 kiB per object) seems high, is this overhead
expected ?
This is a Pacific cluster (16.2.14) if that matters.
Have a nice day,
Loïc.
--
| Loīc Tortay <tortay@xxxxxxxxxxx> - IN2P3 Computing Centre |
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