On Thu, Jan 14, 2016 at 3:28 PM, Dallas Clement
<dallas.a.clement@xxxxxxxxx> wrote:
> Hi, I hope it's ok to ask usage questions on this mailing list.
>
> I have been using fio version 2.2.4 on a Fedora 22 server host to test
> throughput on a 10 GigE LIO iSCSI block device. Up until this point I
> have been testing with Direct I/O (direct=1) and writing directly to
> the block device with filename=/dev/blah (no filesystem). I am seeing
> bandwidth measurements that look reasonable. I next tried to repeat
> this test with Buffered I/O (direct=0) and the bandwidth numbers are
> way too large. Here is a comparison of the sequential write results
> for various block sizes:
>
> bs=4k => direct=95.945 MB/s, buffered=1475.4 MB/s
> bs=512 => direct=495.328 MB/s, buffered=2637.333 MB/s
> bs=2048 => direct=502.093 MB/s, buffered=2663.772 MB/s
>
> As you can see the buffered bandwidth measurements are much larger and
> don't make sense given that not more than 1200 MB/s can be transmitted
> over a 10 Gbps network connection.
>
> Now it's very likely I am doing something stupid and lack
> understanding about how fio works. Someone please enlighten me!
>
> Here is the script I have been using to collect my results for buffered I/O
>
> #!/bin/bash
>
> JOB_FILE=job.fio
>
> cat << EOF > ${JOB_FILE}
> [job]
> ioengine=libaio
> iodepth=\${DEPTH}
> prio=0
> rw=\${RW}
> bs=\${BS}
> filename=/dev/sdc
> numjobs=1
> size=10g
> direct=0
> invalidate=0
> ramp_time=15
> runtime=120
> time_based
> write_bw_log=\${RW}-bs-\${BS}-depth-\${DEPTH}
> write_lat_log=\${RW}-bs-\${BS}-depth-\${DEPTH}
> write_iops_log=\${RW}-bs-\${BS}-depth-\${DEPTH}
> EOF
>
> for RW in read write randread randwrite
> do
> for BS in 4k 512k 2048k
> do
> for DEPTH in 4 32 256
> do
> RW=${RW} BS=${BS} DEPTH=${DEPTH} fio ${JOB_FILE}
> done
> done
> done
>
> I have also tried running this script without the filename=blah
> setting on an XFS formatted block device. I am still seeing inflated
> numbers for this also.
>
> Thanks,
>
> Dallas
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I don't have much experience in testing devices over the network but
you could try increasing size= or leave it out completely to use the
full device size and see how that affects your throughput.
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