I still lost at documentation.
Let's assume I has 8 osd's on single server (osd.[0-7]). I use cephfs
and want to has redundancy 2 (means each peace of data on two osd's) and
spanning of the file across all OSD's (to get some performance on writing).
My expectation: 8x speed on reading, 4x speed on writing (compare to
single drive). [I put aside some overhead]
I'm checking performance of random writes and reads to single file on
mounted cephfs (fio, iodepth=32, blocksize=4k) and I'm getting nice read
performance (1000 IOPS = 125x8, as expected) and just and only 30 iops
on writing. Less then half of single drive performance.
I want to understand what I'm doing wrong.
My settings (for all OSDs they are same, but with different disk name):
[osd.1]
host = testserver
devs = /dev/sdb
osd mkfs type = xfs
I tried to change CRUSH map: "step choose firstn 2 type osd" (for
'data' rule, compare to default), but no effect.
I think here is some huge mistake I making... I need to say 'no more
than two copies of data' and 'block size = 4k when stripping'.
Please help.
Thanks.
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