ReadyNAS104 - iSCSI - Linux

Hi all,

I just purchased a ReadyNAS 104 (well, I know it's not designed for business use...). Anyways, it offers iSCSI.

I created an iSCSI LUN- which is seen by my Linux (Centos6/64) box. I can easily access it. So far it works. It is located on a VMware ESXi 5.0U1 as a VM. The ESX host itself it not very busy. The switch is a HP ProCurve 1810G - 24 GE.

As soon as there is (mid to heavy) I/O on the LUN I'm getting connection errors on my Linux host :-(

 connection1:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4295124378, last ping 4295129378, now 4295134378
 connection1:0: detected conn error (1011)

This error message appears more or less frequently- but as soon as I see it the performance drops! Down to ~50K/sec (even less!) for some minutes...

What I've done for troubleshooting so far:

Google suggests to change some timeout settings so it won't ping (which doesn't affect the issue itself- didn't try)
Disabled the tcp_window_size_scaling as suggested by IBM: http://www-01.ibm.com/support/docview.wss?uid=swg21420774 (reduced the frequency but didn't fix it)
Tried different vNICs (VMXNET2, VMXNET3, E1000)
Enabled Jumbo Frames (everything failed even though it's supported by all devices- strange!)
Did a Wireshark trace (which didn't reveal any issues for me except Wireshark didn't capture some packets, but captured the ACK)

So is there anyone who has at least a single clue what is going on here? Why do I get these messages? Why drops the performance then?

Thanks!

KNEBB