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

[David Tidey]

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