[CentOS] VirtIO disk 'leakage' across guests?

James B. Byrne byrnejb at harte-lyne.ca
Mon Jan 16 20:24:21 UTC 2012


On Mon, January 16, 2012 13:05, James B. Byrne wrote:
> How is it even possible for an
> application running under a httpd service on one guest to
> see anything at all besides the VirtIO storage assigned to
> that guest?
>
> Has anyone else encountered this anomaly?
>

I just cloned a guest instance.  The clone prototype was
set up with a single VirtIO disk of 8Gbs, divided into a
500 Mb boot and a ~7.1Gb root partition.  The root
partition was entirely assigned to the basic vg and two lv
were created, one for swap and one for the actual root
partition.

When the guest was cloned there was only one VirtIO disk
of 8 Gb assigned to it and this was cloned and given a new
name.

When I look at the newly cloned guest instance with
pvdisplay this is what I see:

# pvdisplay
  Couldn't find device with uuid
umrIn6-Np0c-NC4Z-MuUo-5TBj-IKRE-XBU0De.
  --- Physical volume ---
  PV Name               /dev/vda2
  VG Name               vg_vm_centos_6
  PV Size               7.32 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              1874
  Free PE               0
  Allocated PE          1874
  PV UUID              
djM23m-6Yeb-BQ2x-gPh9-ORMt-dX2i-Ou9xBQ

  --- Physical volume ---
  PV Name               unknown device
  VG Name               vg_vm_centos_6
  PV Size               31.25 GiB / not usable 3.97 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              7999
  Free PE               0
  Allocated PE          7999
  PV UUID              
umrIn6-Np0c-NC4Z-MuUo-5TBj-IKRE-XBU0De

When I look at it using vgdisplay then this is what I see:

# vgdisplay
  Couldn't find device with uuid
umrIn6-Np0c-NC4Z-MuUo-5TBj-IKRE-XBU0De.
  --- Volume group ---
  VG Name               vg_vm_centos_6
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  10
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                4
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                1
  VG Size               38.57 GiB
  PE Size               4.00 MiB
  Total PE              9873
  Alloc PE / Size       9873 / 38.57 GiB
  Free  PE / Size       0 / 0
  VG UUID              
qa6jwq-5gTp-6mMH-IWl9-OrEK-HjWc-pbaFsa

What is going on and how do I fix this?  The size of the
ghost pv (31Gb) is showing up as the size of the clone's
vg whereas the pv for the cloned instance is only 8Gb.

I am only using virt-manager to manage disk storage for
these guests and I have no idea why or how this mismash is
happening.  Any ideas?


-- 
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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
Harte & Lyne Limited          http://www.harte-lyne.ca
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Hamilton, Ontario             fax: +1 905 561 0757
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