I was wondering about performance differences between cephfs and rbd, so
I deviced this quick test. The results were pretty surprising to me.
The test: on a very idle machine, make 2 mounts. One is a cephfs mount,
the other an rbd mount. In each directory, copy a humongous .tgz file
(1.5 TB) and try to untar the file into the directory. The untar on the
cephfs directory took slightly over 2 hours, but on the rbd directory it
took almost a whole day. I repeated the test 3 times and the results
were similar each time. Is there something I'm missing? Is RBD that much
slower than cephfs (or is cephfs that much faster than RBD)? Are there
any tuning options I can try to improve RBD performance?
# df -h | grep mnt
10.1.1.150:/ 275T 1.5T 273T 1% /mnt/cephfs
/dev/rbd0 20T 1.5T 19T 8% /mnt/rbd
bash-4.4$ pwd
/mnt/cephfs/test
bash-4.4$ date; time tar xf exceRptDB_v4_EXOGenomes.tgz; date
Fri Jul 2 13:10:01 PDT 2021
real 137m22.601s
user 1m6.222s
sys 35m57.697s
Fri Jul 2 15:27:23 PDT 2021
bash-4.4$ pwd
/mnt/rbd/test
bash-4.4$ date; time tar xf exceRptDB_v4_EXOGenomes.tgz; date
Fri Jul 2 15:38:28 PDT 2021
real 1422m42.236s
user 1m34.198s
sys 38m48.761s
Sat Jul 3 15:21:10 PDT 2021
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