After upgrading our NetWare 6.5 Server from SP7 to SP8 iSCSI throughput to an external NAS appliance dropped to 9 MBytes/s for all read and write requests, which is not acceptable. Yosemite Backup speed suffered even more: The time to take a complete backup run went up from 4,5 to 32,5 hours. We tried tuning several NSS, NCP and NIC parameters, even bought a new PCI Express Dual Gigabit card from Intel, but the transfer rate was totally unaffected by any of these tweaks.
We then looked at the iSCSI changes in NetWare 6.6 Service Pack 8 and simply reverted the following files in SYS:SYSTEM to the ones that came with SP7:
And voila, the transfer speed went up to the values we had before: 28,5 MB/s (reading) and 41 MB/s (writing), Backup speed also went up to about 2 GBytes/min peak as it was before.
Replacing these files does not even need a server restart, dismounting the volume and IOFF / ION does the job. This is of course no recommended Novell prodedure, so you do it on your own risk, but it works for us.