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[Xen-users] number of exportable blockdevices seems to be limited

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: "Ulf Kreutzberg" <Zaphrim@xxxxxx>
  • Date: Fri, 14 Dec 2007 15:51:54 +0100
  • Delivery-date: Fri, 14 Dec 2007 06:52:24 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>

Hi xen-users,

perhaps you can help me with the following:

I am trying to start about 30 (or even more if possible) domU on a host, each 
domU gets 6 partitions (each partion is a logical LVM volume in dom0) and it 
gets two NICs.
In Xen 3.0.3, kernel 2.6.16 32bit, there has been an issue with limited IRQs. I 
now have compiled a Xen3.1, kernel 2.6.18 64bit, and raised nr_dynirqs to 768 
as discussed in a threat on 


Perhaps this was not necessary in my case, but now I do not get any "running 
out of IRQ" messages any more. But if domU 29 oder 30 starts, some vbds seem to 
break down, a Kernel Panic in domU occurs, and maybe some block device of 
another, earlier started domU disappears which causes that domU to hang.
So, finally my question is, is the overall number of exporteable block devices 
limited and is there any (compiling-) option to fix this?

Workarounds like to export a lv as a pv for the domU and making a lvm 
environment there are too dirty and will cost performance, I think.
But any suggestions are welcome. Perhaps some of you have experiences in that. 
If you need more information, just let me know (hw is a dual quadcore xeon 
L5310, 16G RAM on DELL 2950).

Many thanks in advance
and best regards,

Psssst! Schon vom neuen GMX MultiMessenger gehört?
Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger

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