Thursday, March 28, 2013

Platespin Migrate on RHEL

note to self

We had a requirement to convert a number of workloads on RHEV (Red Hat Enterprise Virtualization) environment to vSphere. This is so far unsupported with the vSphere converter tool, and it fails to at the initial step of querying the source system when attempted, complaining about not being able to detect volumes on the source system. (On RHEV, scsi disks are detected as /dev/vdX devices, could be one of the reasons.)

After trying at it for a while, we decided to give PlateSpin Migrate a go, and the results were quite satisfying.

Setting up and starting a workload "copy" is quite straightforward, but could get tricky at times if the source system is running GNU/Linux. (RHEL etc.) PlateSpin supports file based and block based copy methods and for Linux workloads, only the block based method is supported if the migration is to happen while the source is online. Block based copy method depends on a custom kernel module -which has to be build manually, if PlateSpin doesn't come with a matching one for the current kernel.

Process is explained in detail on the below link.

During the conversion, if it throws an error similar to "Could not load driver: Exec format error", then probably the kernel module is not built compatible to the currently running kernel.

To make sure a built module is supported on the current kernel, without going through the trouble of packaging it for PlateSpin, it can be inserted to the running kernel manually. Inserting should not return any error. Loaded module can be viewed and then removed to clean up, by below commands in the order given.

insmod blkwatch.ko
lsmod | grep blkwatch

Even though it looks like a bit more complicated than the vSphere converter, In my opinion, PlateSpin does a far better job! It will be interesting to see how it will handle a conversion where the kernel it self has to be replaced with a different one to be able to run on the destination platform. (eg. Xen to vSphere )

1 comment:

Meera Nagul said...

HI Yajith,

Could you please provide me the step by step document for this error while using platespin migrate.

It could help more..i have followed the link which you are provided in blog. but not sure where am doing mistake.