Xen users - Nov 2008 - Question about certain Xen limits and features

I''ve been away from the Xen community for a while and, unfortunately,
haven''t kept up with its current state.  I''m assembling a
comparison of
virtualization solutions (Xen, VMware, Hyper-V, ...) and I have a few
questions about Xen''s current functionality.  I''d appreciate
it if
somebody would be willing to take the time to answer.  I''m interested
in
the current *released* version (i.e. Xen 3.3 -- not unstable) for
x86_64.  Of course, if you know about on-going work that will change any
of these answers, I''d appreciate knowing that too.

Thanks,
Bruce


(1)  What''s the largest number of "logical processors" that
Xen supports
on the host system?  For me, this translates to cores.  I prefer to keep
hyperthreading out of the picture.  (I believe that this was 126 in 3.3,
but is changing to "unlimited" based on Jan Beulich''s recent
work.  Is
that correct?)

(2a)  What''s the largest host memory that anybody has tested?
(2b)  What''s the expected host memory limit (if somebody was able to
configure a system that large)?

(3a)  What''s the largest guest memory that anybody has tested?
(3b)  What''s the expected guest memory limit (if somebody was able to
configure a system that large)?

(4a)  Does Xen support hot-add of physical hardware to the host system?
If so, which devices?
(4b)  Hot remove?

(5a)  What''s the maximum # of virtual NICs per guest?
(5b)  What''s the maximum # of virtual HBAs per guest?
(5c)  What''s the maximum # of LUNs per guest?

(6)  What''s the maximum # of powered-on guests per system?


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I have Ubuntu 8.04 Dom0 and CentOS 5.2 DomU. I want to be able to mount the
image file of the CentOS DomU in the Ubuntu Dom0 to copy some stuff onto it.

I figured I could do it this way...

Make sure DomU was destroyed.

losetup /dev/loop1 /xen/test/test.img

using ''p'' in fdisk /dev/loop1 gives me what I would expect...
two partitions....

/dev/loop1p1 .... Linux
/dev/loop1p2 .... Linux LVM

when I run pvscan, it returns the error "no matching physical volumes
found".

When I run pvcan -vvv it appears to look at /dev/loop1 but simply states that no
label is found.

Under LVM on both systems, I did a ''version'' command:-

Ubuntu Dom0

LVM     2.02.26 2007-06-15
Lib        1.02.20 2007-06-15


CentOS DomU

LVM    2.02.32-RHEL5    2008-03-04
Lib       1.02.24                  2007-12-20

Am I doing something wrong or is the problem with the slight mis-match of
versions?

Thanks in advance,

Ian.



      

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On Thu, 6 Nov 2008, Ian Murray wrote:
> I have Ubuntu 8.04 Dom0 and CentOS 5.2 DomU. I want to be able to mount the
image file of the CentOS DomU in the Ubuntu Dom0 to copy some stuff onto it.
>
> I figured I could do it this way...
>
> Make sure DomU was destroyed.
>
> losetup /dev/loop1 /xen/test/test.img
>
  now you can use kpartx tool
kpartx -a /dev/loop1
  it will create the following device nodes
/dev/mapper/loop1p1
/dev/mapper/loop1p2
  which you can now access as normal block devices
  once finished use
kpartx -d /dev/loop1
> using ''p'' in fdisk /dev/loop1 gives me what I would
expect... two partitions....
>
> /dev/loop1p1 .... Linux
> /dev/loop1p2 .... Linux LVM
>
> when I run pvscan, it returns the error "no matching physical volumes
found".
>
> When I run pvcan -vvv it appears to look at /dev/loop1 but simply states
that no label is found.
>
> Under LVM on both systems, I did a ''version'' command:-
>
> Ubuntu Dom0
>
> LVM     2.02.26 2007-06-15
> Lib        1.02.20 2007-06-15
>
>
> CentOS DomU
>
> LVM    2.02.32-RHEL5    2008-03-04
> Lib       1.02.24                  2007-12-20
>
> Am I doing something wrong or is the problem with the slight mis-match of
versions?
>
> Thanks in advance,
>
> Ian.
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