Hello, all. We are testing disk I/O perfomance using fio tool. I've measured performance on qcow2 image mounted to nb0 device. I run tests and launch iostat -x 1 command to browse I/O operations. Test consists of sequential read operations with 1 MB size. I've get following output.
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s sda 0.00 5.00 0.00 677.00 0.00 22812.00 sdb 0.00 0.00 0.00 545.00 0.00 0.00 dm-0 0.00 0.00 0.00 674.00 0.00 22784.00 dm-1 0.00 0.00 0.00 7.00 0.00 28.00 dm-2 0.00 0.00 0.00 0.00 0.00 0.00 nb0 0.00 0.00 432.00 182.00 55296.00 23296.00 So, reading produce a lot of write operations. What is the reason why these write operations occured? How to determina block size that qemu operates , because if i've writtien 55 mb with 1 mb blocks i should get 55 operations instead of 432. Kind regards, Gleb Stepanov.
