Did you test with the Demo-CD - DSS yet? Also send your results to support with new logs.
In blockIO we use only cache specified for devices - fileIO use filesystem cache and devices cache. The default maximum of device cache in 32bit kernel is limited actually to about 1GB.

This was emailed to me today asking them to perform some test to verify there speed with iSCSI-R3 with 4x1Gb - MPIO from Microsoft. There must be something that needs to be tweaked on the hardware (firmware, NIC driver....), they testing with the Demo-CD then send the logs using the same ticket number.

hardware specification

Target

iSCSI-R3 Ent. Ver. 2.30 build 2820
CPU 2 x QUAD (Xeon) 2Ghz
Ram: 2Gb
Controller: LSI Logic SAS
Disc: 8x36GB (Raid0)
NIC: Intel Corporation Pro/1000 PT Quad Port LP server Adapter
Information: SSR212mc2

Client

Windows 2003 server with service pack 1
CPU: Xeon 1.86 Ghz
Ram: 2Gb
NIC: Intel Corporation Pro/1000 Pt Quat Port LP server Adapter
initiator: Windows iSCSI Initiator 2.05 build 2392


Performance Result

IOmeter MPIO , out_io=100 row-device
1worker 64k seq write io=3963,72 mb=247.73 cpu=70.78 1worker 64k seq read
io=5951,91 mb=371,99 cpu=81,76

2workers 64k seq write io=3776,17 mb=236.01 cpu=76,43 2workers 64k seq read
io=5368,14 mb=335,51 cpu=75,64

1worker 512 seq write io=700,37 mb=0.34 cpu=2,35 1worker 512 seq read
io=9264,68 mb=4,52 cpu=21,42

2workers 512 seq write io=1478.56 mb=0.72 cpu=5,76 2workers 512 seq read
io=13180,47 mb=6,44 cpu=22,88