Documentation #48156
closeddoc/rados: monitoring.rst -- UNDER COMPR field out-of-date
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Description
Here is the text that must be updated:
BEGIN QUOTED TEXT
Here is another ‘ceph df detail’ sample output where 500K object was compressed (partially, due to unaligned object size - 448K only). So 384K at USED COMPR is caused by 3x128K allocation units for keeping compressed data at 3 replicas. And 1.31M at UNDER COMPR column denotes 3x448K blocks of user data compressed at 3 replicas. And this requires in total (see USED) 576K = 3x128K + 3x64K (=ROUND_UP_TO(500K - 448K, 64K)):
CLASS SIZE AVAIL USED RAW USED %RAW USED
ssd 202 GiB 200 GiB 2.0 GiB 2.0 GiB 1.00
TOTAL 202 GiB 200 GiB 2.0 GiB 2.0 GiB 1.00
--- POOLS ---
POOL ID PGS STORED (DATA) (OMAP) OBJECTS USED (DATA) (OMAP) %USED MAX AVAIL QUOTA OBJECTS QUOTA BYTES DIRTY USED COMPR UNDER COMPR
device_health_metrics 1 1 242 KiB 15 KiB 227 KiB 4 251 KiB 24 KiB 227 KiB 0 297 GiB N/A N/A 4 0 B 0 B
cephfs.a.meta 2 32 6.8 KiB 6.8 KiB 0 B 22 96 KiB 96 KiB 0 B 0 297 GiB N/A N/A 22 0 B 0 B
cephfs.a.data 3 32 0 B 0 B 0 B 0 0 B 0 B 0 B 0 99 GiB N/A N/A 0 0 B 0 B
test 4 32 22 MiB 22 MiB 50 KiB 248 19 MiB 19 MiB 50 KiB 0 297 GiB N/A N/A 248 0 B 0 B
END QUOTED TEXT
The core idea here is fine, but the text doesn't match with the example "ceph df" output.
cf. https://github.com/ceph/ceph/pull/37539
This matter was raised in direct response to that one.
Updated by Zac Dover over 3 years ago
Add these notes to the example output of "ceph df" when the example and text are ready.
.. note:: The numbers in the POOLS section are notional. They are not
inclusive of the number of replicas, snapshots or clones. As a result,
the sum of the USED and %USED amounts will not add up to the
USED and %USED amounts in the RAW section of the
output.
.. note:: The MAX AVAIL value is a complicated function of the
replication or erasure code used, the CRUSH rule that maps storage
to devices, the utilization of those devices, and the configured
``mon_osd_full_ratio``.
Updated by Zac Dover over 3 years ago
- Status changed from New to Resolved
- Pull request ID set to 37539
This was resolved some time ago (10 Nov 2020), but I am only now doing the bookkeeping on this matter.