> From: [email protected] [mailto:[email protected]] On > Behalf Of Pal, Laszlo
> Finally I've figured out how to use FIO :) now, I can measure several > things, so I've started to get IOPS data for our hardware. The graphs > looks good, however I can see a very strange discrepancy at seq_write > part > [global] > ioengine=libaio Without iodepth >1, you'll effectively be doing synchronous i/o, so there's no benefit to using libaio. If you're interested in throughput (not latency), set iodepth to 512, which will likely be greater than whatever is in the drive/controller/OS. > buffered=0 Don't need this if you specify- > direct=1 > bs=4k > blocksize_range=1k-64k AFAIK, blocksize_range will supersede bs. Also depending on the drive (what type?), this can cause mis-aligned writes which massively slow the overall process. I've mostly seen this with 4kn and 512e SSDs. You can examine that by trying blockalign=4k. > size=2048m I usually use a runtime spec instead of size, and also set fill_device=true. [snip] > > the results as the follows (iops or MB/s?) > Random Read -- 86 > Random Write -- 77 > Sequential Read -- 2170 > Sequential Write -- 45 > I have two questions again. > The parameters above are good approach to determine IOPS for this system? See above :) > What can be the reason of the huge difference between Seq_read and Seq_write? Many things. First off, is this a block level test or is there a file system involved? What drives? What controller? RAID? z! -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
