iscsi_initiator 2.2.2 slow to write and read

[Ivan Voras]

Jiansong Liu wrote:
> On Wed, Jul 8, 2009 at 1:36 AM, Gary Palmer <gpalmer at freebsd.org> wrote:
> 
>> On Tue, Jul 07, 2009 at 07:05:03PM +0800, Jiansong Liu wrote:
>>> Hello All,
>>>
>>> I downloaded the latest iscsi_initiator 2.2.2 from Danny's FTP,
>>> and compile kernel and iscontrol with 7.2 STABLE GENERIC config, only got
>>> about 800KB/Sec speed to a DELL MD3000i disk array, I searched in
>>> this malling list and found a patch, but it seems is not for this version
>>> (2.2.2), any advice would be great appreciated.
>>>
>>> here are some details about my system:
>>>
>>> # sysctl net.iscsi
>>> net.iscsi.driver_version: 2.2.2
>>> net.iscsi.isid: ???DIB00
>>> net.iscsi.sessions: 1
>>> net.iscsi.0.targetname:
>>> iqn.1984-05.com.dell:powervault.md3000i.60024e80004e71a9000000004a011120
>>> net.iscsi.0.targeaddress: 192.168.4.182
>>> net.iscsi.0.stats: recv=594 sent=594 flags=0x0000039f pdus-alloc=16
>>> pdus-max=16 cws=426 cmd=157 exp=157 max=300 stat=159 itt=157
>>> net.iscsi.0.douio: 0
>>> net.iscsi.0.pid: 754
>>>
>>> # cat /etc/iscsi.conf
>>> scpstorage01 {
>>>         initiatorname =iqn.2005-01.il.ac.huji.cs::static01.com
>>>         TargetName
>>>
>>  =iqn.1984-05.com.dell:powervault.md3000i.60024e80004e71a9000000004a011120
>>>         TargetAddress =192.168.4.182:3260,1
>>>          tags =4
>>> }
>> I'm no expert, but if that "tags" line refers to SCSI tags then that
>> number is too small.  Try increasing it and see if that helps to
>> address the problem.
>>
>> Regards,
>>
>> Gary
>>
> 
> Hi Gary,
> 
> Thanks for the advice, I have tried set tags to 32 and 64,
> but it could not get more performance on IO (90MB write and 56MB read).
> I think the writing is good enough for my application, but the reading still
> is a problem.
> 
> # dd if=/home/mogdata/test.foo of=/dev/null
> 2048000+0 records in
> 2048000+0 records out
> 1048576000 bytes transferred in 17.670549 secs (59340318 bytes/sec)

Are you really reading sector by sector? Try adding bs=1m to the dd line.

There is something else you can try to increase sequential reading, if 
that's what you're interested in: increase the vfs.read_max sysctl to 32 
or 64.

On the other hand, it will do nothing to improve, and may harm random 
read performance. Test with your actual application before drawing 
conclusions.