XEN: Howto migrate loopback file based disk images to blktap tap:aio

This document (7000716) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 10 Service Pack 2

Situation

Migrate a loopback file based disk image to a blktap tap:aio disk image without reinstalling the DomU.

Resolution

Backup current DomU configuration:
xm list <DomU_ID> -l > /tmp/vm1.conf
Edit disk device section of the configuration file:
vi /tmp/vm1.conf

# Configuration example

(device
(vbd
(unamefile:/xen/vm1/disk0)
(uuid d2cb4a14-ecbd-6034-3d4c-7866bfd4b60e)
(mode w)
(devxvda:disk)
(backend 0)
(bootable 1)
)
)

# Change to

(device
(tap
(uname tap:aio:/xen/vm1/disk0)
(uuid d2cb4a14-ecbd-6034-3d4c-7866bfd4b60e)
(mode w)
(dev xvda:disk)
(backend 0)
(bootable 1)
)
)
Delete old DomU
xm delete <DomU_ID>
Load new configuration
xm new -F /tmp/vm1.conf
Start new DomU
xm start <DomU_ID>

Additional Information

The advantage of the blktap is a better performance compared to disk images accessed through loopback. The blktap driver is supported as of SLES10 SP2, however for NetWare this should only be used on NW65SP8.

Disclaimer

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