How to correctly benchmark sequential read speeds on 2.5" hard drive with fio on FreeBSD?

Question

Like suggested in https://askubuntu.com/a/991311 I tested the read speed of a 2.5" spinning hard drive on a TrueNAS/FreeBSD system.

For "Sequential READ speed with big blocks":

fio --name TEST --eta-newline=5s --filename=fio-tempfile.dat --rw=read --size=500m --io_size=10g --blocksize=1024k --ioengine=posixaio --fsync=10000 --iodepth=32 --direct=1 --numjobs=1 --runtime=60 --group_reporting

I got 8037 MB/s.

I don’t believe this.

I did replace liaio with posixaio, do I need another engine?

Answer 1

I think you are testing the speed of your system's filesystem cache because you are only fsyncing every 10000 I/Os (so that's every 9GBytes). Does your speed change if you use you choose use the direct=1 option?