Let's benchmark single disk read performance:

1. Drop caches:

        # echo 3 > /proc/sys/vm/drop_caches

2. Use dd to read from the file, deleteme, which we created during the write test. We will read the deleteme file to /dev/null with iflag set to direct:

        # dd if=/var/lib/ceph/osd/ceph-0/deleteme of=/dev/null bs=10G
         count=1 iflag=direct

Ideally, you should repeat step 1 and step 2 a few times and take the average value. In our case, the average value for read operations comes to be 133 MB/s, as shown in the following screenshot: