istgt performance issue when copying large files (1G plus)

[Daisuke Aoyama]

Hi,

>I am using FreeBSD 8.2 with the very latest istgt version 20110103.

I submitted new version of istgt 20110223. You can install it from ports.
If you use QueueDepth, I recommend upgrading to 20110223.

>I am using istgt to expose a zfs volume to a windows client.

Which mode did you use? Latest istgt has three modes.

1) default or QueueDepth=0
  This mode uses single thread per connection.
2) QueueDepth=32 or any choice except zero (20100707 compatible)
  This mode uses one thread per connection and one thread per LUN.
3) QueueDepth with -m1 command line option (experimental)
  This mode uses two threads per connection and one thread per LUN.

The experimental mode is intended to be used by Hexa core CPU and 10Gbps 
link,
and to be improved for 4KB random concurrent I/O.
Single core CPU is not supported under this mode.

The result of FreeNAS 0.7.2 with new istgt is here:
http://shell.peach.ne.jp/aoyama/archives/1384

Regards,
Daisuke Aoyama

--------------------------------------------------
From: "David Tidey" <david.tidey at tidey.com>
Sent: Thursday, January 27, 2011 7:35 AM
To: <freebsd-scsi at freebsd.org>
Subject: istgt performance issue when copying large files (1G plus)

> Hello,
>
> I am using FreeBSD 8.2 with the very latest istgt version 20110103.
>
> I am using istgt to expose a zfs volume to a windows client.
>
> When running a disk benchmark which writes 10 files of around 40mb each
> performance is 60-70Mb/sec.
>
> When I copy a video file over over 1G performance starts off fast - 
> 60Mb/sec
> plus. After copying a couple of 100Mb performance starts to drop to less
> than 10Mb/sec.
>
> Exposing the same disks using samba gives performance of 40-50Mb/sec with 
> no
> drop off problems
>
> I therefore am assuming this is an istgt problem
>
> Any views on how to diagnose this?
>
> David
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