Fio

1

I would suggest using fio as I described in answer https://askubuntu.com/a/991311/50254

The fio allows you to get more info about the distribution of latencies for different work loads (anything between single threaded huge sequential writes QD32 and mixed random read and write 4k QD1 with multiple threads).

I think that if you assume that hardware has higher latency than previously, you should test single threaded random 4k read QD1 (this is the most latency sensitive operation that I can think):

fio --name TEST --eta-newline=5s --filename=fio-tempfile.dat --rw=randread --size=500m --io_size=10g --blocksize=4k --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=1 --runtime=60 --group_reporting

That will create test file fio-tempfile.dat in the current working directory so make sure that you first change to device you want to test. (If you want to test raw device performance instead of performance with a file system, you can use raw device as the filename. You're going to lose current contents of said device, though.)

You can also test the same thing with writing instead of reading data:

fio --name TEST --eta-newline=5s --filename=fio-tempfile.dat --rw=randwrite --size=500m --io_size=10g --blocksize=4k --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=1 --runtime=60 --group_reporting

If you see huge increase in latency with write you can be pretty sure that old firmware allowed write back cache and the new firmware does not allow that. Unless you have battery backed RAID controller or correctly configured UPS, you do not want write back cache if you consider your data important.

share  edit