IBM Server x3550 7978 / aacraid / scsi hung

Hello Team,
I'm new here in this issue board. I searched for my "upgrade from XS 6.5 to XS 7 Problem" and found two issue numbers => XSO-466 / XSO-562.

I have the (same) issue, reported here in the past in XSO-466 and XSO562.

I have three of the described x3550 Servers. Two of them a running with XS 6.5 in a pool fine.
On the third standalone one i have installed XS 6.5 (RAID 5 / whole Disk / 4 sas-devices), to test (probe) the upgrade procedure from XS 6.5 to XS 7. On this (third) Server before boot XS 7 i have added (touch) the /var/preserve/safe2upgrade (only as Information).
While booting then XS 7 (downloaded mid of August 2016 from xenserver.org) from cd-drive there are Messages that describe that there is a problem with the RAID Controller (aacraid / scsi hung).
Is there a possibility to solve this?.

When not, i have to buy three new Server for my test Environment. But i don't wan't this

I'm working as a Consultant and the XenServer and my lab are the best choice for me to verify and find Solutions in every day situations.

Best regards and greetings from Germany
Matthias