Need to Migrate RDM to new Lun - will Storage vMotion work???

[Ryzz]

Hi,

As the topic suggests, I have an EMC san presenting luns into VMware which are used as RDM's in Windows 2008 Servers.

Due to space constraints I need to move the RDM's onto new luns in a different RAID pool. I have presented the new LUNS into ESX, however I cant think of an easy way to migrate the RDM luns to the new luns.

Is it possible to use Storage vMotion to migrate all the RDM Data to a new lun? Moving the data through Windows isnt an option, it must be done at the ESX layer.

Im open to any suggestions, thx in advance!!!

[thakala]

Can't you do LUN migration on EMC storage array? At least on CX4 it works just fine.

If your RDM mappings are in virtual compatibility mode you can use storage vMotion to migrate RDMs as VMDKs but I am not too sure about migrating as RDM from LUN to another. If you are using physical compatibility mode RDM you cannot storage vMotion RDM at all, only mapping file will move.

Tomi

http://v-reality.info

[kgottleib]

I believe this can be done, why?  I just converted a physical mode RDM to a virtual disk with the following command: 

vmkfstools -i servername_1.vmdk  /vmfs/volumes/newlocation/servername.vmdk

In this example, the source disk which is the physical LUN, is represented by the pointer file servername_1.vmdk which points to servername_1-rdmp.vmdk which is the actual RDM mapping to the LUN.

Given that you can do the above, you should also be able to clone the LUN to another disk format other than a basic vitual disk, like a virtual or physical mode RDM, as follows:

vmkfstools -i servername_1.vmdk -d rdmp:/vmfs/devices/disks/vml.xxxxxxxxxxxxxxxxxxx

In this string, the source disk is once again servername_1.vmdk which is the physical LUN, the "-d rdmp "is the disk format you are cloning the data to, the /vmfs/devices/disks/vml.xxxxxxxx is the physcial path to the LUN and the vml.xxxxxxxxxx is a really pain in the ass long and unfriendly # that VMware gets from the storage array.  Note, it is difficult to determine which vml.xxxx is which LUN.  try entering ls -lh from the /vmfs/devices/disks directory and you will most likley be able to figure out which is the right one based on the lun size.  Otherwise, you might need to google how to identify this.

I am actually about to test this process out this morning.

[Satyavmware]

There are two ways to perform this.

Option-1:

     Cold Migration (power-off the VM and SVMotion) gives you a way to move all your VMs (with RDM disks) from one Storage Array/LUN to other.

     But the problem here is your RDM disks will be converted to virtual disks.

     Later you can clone this virtual disk to a RDM using vmkfstools. Then remove the vmdk and add this RDM to the VM.

Option- 2 :

     Remove (not delete) the RDM from the VM.

     SVMotion the VM to other Storage Array, then clone the RDM from Storage Array/LUN 1 to Storage Array/LUN 2 (using vmkfstools).

     Attach this RDM to the VM.

Please let me know this answers your query or you need more info?

[kgottleib]

You can't migrate RDM to a new LUN without converting to a virtual disk when using storage vmotion.  You must use vmkfstools -i 

Please review a post a put up last week that provides full details on how this is done.  I have seen too many gurus try to provide answers to this and all they do is confuse the matter.

http://communities.vmware.com/message/1719931#1719931

[malaysiavm]

you should consider the SAN copy function from your EMC box if you do have 1. or else, I will suggest you perform the LUN base migration solution from OS level or power off the VM to perform the block base replication of the RDM LUN over to the new LUN since you may end up would like to keep the LUN running with RDM after that.