Slow iSCSI performance

[Philip Murray]

Hi,

I'm trying to use the new iSCSI initiator (thanks!) with 7, but I'm  
getting dismal performance. A simple dd will will max out at about 2MB/ 
sec, and untarring the likes of the ports tree is a painful task.

The target is another FreeBSD 7 machine running the NetBSD target  
daemon from ports exporting a ZVOL from ZFS (also tried with a file on  
UFS).


It'll start off relatively fast and then suddenly dies after a few  
seconds, and then eventually will start again:

      tty             da0              da1             
pass0             cpu
  tin tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy  
in id
    0   78 63.90 494 30.80   0.00   0  0.00   0.00   0  0.00   0  0   
5  2 93
    0   77 63.89 575 35.90   0.00   0  0.00   0.00   0  0.00   0  0   
8  3 89
    0   77 63.86 581 36.26   0.00   0  0.00   0.00   0  0.00   0  0   
5  4 91
    0   77 63.64 268 16.64   0.00   0  0.00   0.00   0  0.00   0  0   
3  2 95
    0   77  0.00   0  0.00   0.00   0  0.00   0.00   0  0.00   0  0   
0  0 100
    0   77  0.00   0  0.00   0.00   0  0.00   0.00   0  0.00   0  0   
0  0 100


The two hosts are connected with GbE, and iperf can saturate it  
without trouble (~987Mb/sec in both directions).

Any ideas where to start looking for the culprit?

Cheers

Phil