RE: [Iscsitarget-devel] Abort Task ?

[Ming Zhang <blackmagic02881@gmail.com>]

On Thu, 2007-10-18 at 17:03 -0400, Ross S. W. Walker wrote:
> BERTRAND Joël wrote:
> > 
> > BERTRAND Joël wrote:
> > >     I can format serveral times (mkfs.ext3) a 1.5 TB volume 
> > over iSCSI 
> > > without any trouble. I can read and write on this virtual 
> > disk without 
> > > any trouble.
> > > 
> > >     Now, I have configured ietd with :
> > > 
> > > Lun 0 Sectors=1464725758,Type=nullio
> > > 
> > > and I run on initiator side :
> > > 
> > > Root gershwin:[/dev] > dd if=/dev/zero of=/dev/sdj bs=8192
> > > 479482+0 records in
> > > 479482+0 records out
> > > 3927916544 bytes (3.9 GB) copied, 153.222 seconds, 25.6 MB/s
> > > 
> > > Root gershwin:[/dev] > dd if=/dev/zero of=/dev/sdj bs=8192
> > > 
> > >     I'm waitinfor a crash. No one when I write these lines. 
> >    I suspect 
> > > an interaction between raid and iscsi.
> > 
> > 	I simultanely run :
> > 
> > Root gershwin:[/dev] > dd if=/dev/zero of=/dev/sdj bs=8192
> > 8397210+0 records in
> > 8397210+0 records out
> > 68789944320 bytes (69 GB) copied, 2732.55 seconds, 25.2 MB/s
> > 
> > and
> > 
> > Root gershwin:[~] > dd if=/dev/sdj of=/dev/null bs=8192
> > 739200+0 records in
> > 739199+0 records out
> > 6055518208 bytes (6.1 GB) copied, 447.178 seconds, 13.5 MB/s
> > 
> > 	without any trouble.
> 
> The speed can definitely be improved. Look at your network setup
> and use ping to try and get the network latency to a minimum.
> 
> # ping -A -s 8192 172.16.24.140
> ....
> --- 172.16.24.140 ping statistics ---
> 14058 packets transmitted, 14057 received, 0% packet loss, time 9988ms
> rtt min/avg/max/mdev = 0.234/0.268/2.084/0.041 ms, ipg/ewma 0.710/0.260 ms
> 
> You want your avg ping time for 8192 byte payloads to be 300us or less.
> 
> 1000/.268 = 3731 IOPS @ 8k = 30 MB/s

he use normal dd, which in turn use page cache and read ahead, so actual
request size at scsi layer can be much larger than 8k....


> 
> If you use apps that do overlapping asynchronous IO you can see better
> numbers.
> 
> -Ross
> 
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-- 
Ming Zhang


@#$%^ purging memory... (*!%
http://blackmagic02881.wordpress.com/
http://www.linkedin.com/in/blackmagic02881
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