Hi Pasi,

Thank you very much for your reply.

> > I was testing the performance of open-iscsi initiator with IET target
> > over a 100Mbps Ethernet link with emulated rtt.  What I did was to do
> > raw disk sequential write by
>
> > $ dd if=/dev/zero of=/dev/sdb bs=1024 count=1048576
>
> Did you also try with bigger block sizes? 1k blocks are pretty small.
>
> try bs=1024k to see if it makes a difference.


I tried bs = 1024k and the throughput is improved, but not much... It
goes from 7.2MB/s to 8.0MB/s at a rtt of 16ms. And again, over 90% of
the TCP segments on the wire was only of 1448 bytes...


> dd will use only one outstanding IO, so you have wait for rtt
> milliseconds after every IO for the ack.. so that definitely slows you
> down a lot when rtt gets bigger.
>
> Try using some benchmarking tool that can do multiple outstanding IOs..
> for example ltp disktest.
>

And I tried ltp disktest, too. But I'm not sure whether I used it
right because the result was a little surprising...

I did

disktest -w -S0:1k -B 1024 /dev/sdb

(/dev/sdb is the iSCSI device file, no partition or file system on it)

And the result was:

| 2010/01/05-02:58:26 | START | 27293 | v1.4.2 | /dev/sdb | Start
args: -w -S0:1024k -B 1024 -PA (-I b) (-N 8385867) (-K 4) (-c) (-p R)
(-L 1048577) (-D 0:100) (-t 0:2m) (-o 0)
| 2010/01/05-02:58:26 | INFO  | 27293 | v1.4.2 | /dev/sdb | Starting
pass
^C| 2010/01/05-03:00:58 | STAT  | 27293 | v1.4.2 | /dev/sdb | Total
bytes written in 85578 transfers: 87631872
| 2010/01/05-03:00:58 | STAT  | 27293 | v1.4.2 | /dev/sdb | Total
write throughput: 701055.0B/s (0.67MB/s), IOPS 684.6/s.
| 2010/01/05-03:00:58 | STAT  | 27293 | v1.4.2 | /dev/sdb | Total
Write Time: 125 seconds (0d0h2m5s)
| 2010/01/05-03:00:58 | STAT  | 27293 | v1.4.2 | /dev/sdb | Total
overall runtime: 152 seconds (0d0h2m32s)
| 2010/01/05-03:00:58 | END   | 27293 | v1.4.2 | /dev/sdb | User
Interrupt: Test Done (Passed)

As you can see, the throughput was only 0.67MB/s and only 85578
written in 87631872 transfers...
I also tweaked the options with "-p l" and/or "-I bd" (change seek
pattern to linear and/or speficy IO type as block and direct IO) but
no improvement happened...

There must be something I've done wrong... Could you maybe help me out
here?

Thanks a lot!

jack

--

You received this message because you are subscribed to the Google Groups 
"open-iscsi" group.
To post to this group, send email to open-is...@googlegroups.com.
To unsubscribe from this group, send email to 
open-iscsi+unsubscr...@googlegroups.com.
For more options, visit this group at 
http://groups.google.com/group/open-iscsi?hl=en.


Reply via email to