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