Fio

The flexible IO (fio) utility can be used to quickly benchmark the filesystem IO performance.

Quick start

Select one of the following commands to run.

Description	Command
Sequential read test, 1MB block size, 1 thread, 1 queue	# fio \ --ioengine=libaio \ --direct=1 \ --randrepeat=0 \ --refill_buffers \ --end_fsync=1 \ --filename=/home/lleung/.kdiskmark.tmp \ --name=sequential-read-8-queues-1-thread \ --rw=read \ --size=1073741824 \ --bs=1024k \ --iodepth=1 \ --numjobs=1 \ --iodepth=8 \ --runtime=5

Understanding the results

Results you get after running fio looks like something below:

Starting 1 process
sequential-read-8-queues-1-thread: Laying out IO file (1 file / 1024MiB)
Jobs: 1 (f=1): [R(1)][100.0%][r=241MiB/s][r=241 IOPS][eta 00m:00s]
sequential-read-8-queues-1-thread: (groupid=0, jobs=1): err= 0: pid=137965: Thu Jul 28 15:41:32 2022
  read: IOPS=190, BW=191MiB/s (200MB/s)(957MiB/5014msec)
    slat (usec): min=105, max=881, avg=222.28, stdev=54.72
    clat (msec): min=3, max=426, avg=41.63, stdev=63.38
     lat (msec): min=3, max=427, avg=41.86, stdev=63.38
    clat percentiles (msec):

• slat - submission latency. This is the time it took to submit the I/O. This could be useful if you need to determine if you need to tune the IO scheduler (eg. from spinning disk to SSD) or if there's a network issue for network based filesystems.
• clat - completion latency. This is the time between submission and completion.

Other notes

Drop caches

You might want to drop caches before doing a test to avoid skewed results by running: echo 1 > /proc/sys/vm/drop_caches

Change the output format

Use the --output-format=json option to change the output format to json.