Hi,
AWIK, the read latency primarily depends on HW latency,
not much can be tuned in SW. Is that right?
I ran a fio random read with iodepth 1 within a VM backed by
Ceph with HDD OSD and here is what I got.
=================
read: IOPS=282, BW=1130KiB/s (1157kB/s)(33.1MiB/30001msec)
slat (usec): min=4, max=181, avg=14.04, stdev=10.16
clat (usec): min=178, max=393831, avg=3521.86, stdev=5771.35
lat (usec): min=188, max=393858, avg=3536.38, stdev=5771.51
=================
I checked HDD average latency is 2.9 ms. Looks like the test
result makes perfect sense, isn't it?
If I want to get shorter latency (more IOPS), I will have to go
for better disk, eg. SSD. Right?
Thanks!
Tony