test cas with sysbench randwr cas

[bugme1024]

Question

why there is some io to hdd device? It is caused by fsync?

reproduce step:
0. mkfs.exte /dev/cas1-1

1. mount /dev/cas1-1 /data
2. execute in /data: sysbench --test=fileio --threads=16 --file-block-size=16k --file-total-size=100G --file-test-mode=seqrd --report-interval=1 prepare
   3.execute in /data:
   sysbench --test=fileio --num-threads=16 --file-block-size=16k --file-total-size=100G --file-test-mode=rndwr --report-interval=1 --file-extra-flags=direct --time=60 run

Motivation

i want to improve performance with fsync call.

Your Environment

• OpenCAS version (commit hash or tag):
  casadm --version
  +=========================+======================+
  | Name | Version |
  +=========================+======================+
  | CAS Cache Kernel Module | 21.06.2.0550.release |
  | CAS Disk Kernel Module | 21.06.2.0550.release |
  | CAS CLI Utility | 21.06.2.0550.release |
  +=========================+======================+
• Operating System: centos 7.6
• Kernel version:
• Cache device type (NAND/Optane/other): nvme ssd
• Core device type (HDD/SSD/other): hdd
• Cache configuration:
• • Cache mode: (default: wt) writeback
• • Cache line size: (default: 4)
• • Promotion policy: (default: always)
• • Cleaning policy: (default: alru)
• • Sequential cutoff policy: (default: full)
• Other (e.g. lsblk, casadm -P, casadm -L)