Hi,

I'm experiencing performance issues while exporting a ZVOL via iSCSI. The 
initiator I tried is the Microsoft sw initiator, 2.08 under win xp sp3.
Regarding the target, a little regression is needed here. At first, I tried 
with the standard iscsitgtd shipped with solaris 10 u6. Tried exporting:

- a raw device created with vxvm
- a raw disk slice
- a raw zvol

Results were quite good, except for the raw zvol. High load average, occasional 
hangs, low throughput.

Then I decided to give COMSTAR a try, so I installed opensolaris b107/SPARC. 
Tried exporting

- a raw disk slice
- a raw zvol

Result is very good with the raw disk slice; despite the not-so-powerful 
machine (we're talking about a single 450mhz Ultra 60) I was able to achieve 
near wire speed performance (network is fast ethernet) and relatively low cpu 
usage (~20% sys cpu time).
Exporting the zvol exhibits the same issues as in sol10 u6, even if the cpu 
usage in this case wasn't so high (~40% of sys cpu time, 55% idle); throughput 
around 25-30 mbit/s.
I've tried anything, ranging from disabling zfs checksumming/ARC/ZIL to 
tweaking network settings (disabled nagle alg on both target/initiator at 
first).

Here are the specs of the target box:

System Configuration:  Sun Microsystems  sun4u Sun Ultra 60 UPA/PCI 
(UltraSPARC-II 450MHz)
System clock frequency: 113 MHz
Memory size: 2048 Megabytes

Disks are maxtor SATA drives hooked to an LSI-3041X (no volumes configured on 
the HBA, so the OS sees the raw disks). 

Any ideas, anyone?

Regards,
Simone.
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