We're considering using bluestore compression for some of our data, and
I'm not entirely sure how to interpret compression results. As an
example, one of the osd perf dump results shows:
"bluestore_compressed": 28089935,
"bluestore_compressed_allocated": 115539968,
"bluestore_compressed_original": 231079936,
Am I right to interpret this as "Originally 231079936 bytes (231GB) were
compressed to 28089935 bytes (28GB) and were stored in 115539968 bytes
(115GB)". If so, why is there such a huge discrepancy between the
compressed_allocated and compressed numbers (115GB vs 28GB)?
Also, ceph df detail also shows some compression stats:
POOL ID STORED OBJECTS USED
%USED MAX AVAIL QUOTA OBJECTS QUOTA BYTES DIRTY
USED COMPR UNDER COMPR
cephfs_data_ec63_c 5 1.2 TiB 311.93k 1.7 TiB
0.02 5.4 PiB N/A N/A 311.93k 116
GiB 232 GiB
Would this indicate that the compressed data takes up exactly half the
space (which coincides with what the osd's are saying)? It is odd that
the allocated numbers are always half the original numbers ...
This is ceph Nautilus with all the defaults for compression (except
turning it on for the pool in question). Any insights here would be
appreciated.
Thanks,
Andras
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