[Xen-users] overhead of Xen when using iSCSI

[Siim Vahtre <siim_@xxxxxxxx>]

I have setup iSCSI targets (with open-iscsi) to dom0 (Xen 3.1), which are 
exported to paravirtualized guests:
disk = [ 'phy:/dev/iscsi/test0,hda1,w' ]

Everything works fine, but there is huge overhead. If I write to iSCSI 
device in dom0 I get write speeds of about 29Mbytes/s, but if I write to 
/dev/hda1 in domU I only get about 14Mbytes/s.
This kind of performance drop does not happen with regular disks or even 
NBD - they have some overhead but not 50% like I have with iSCSI.
I have searched the list and I know that some people have successfully run 
setup similar to mine, so I'd like to ask if anyone could please share 
their experience and tell me if 50% performance drop is really normal.
Thanks!

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