Garry White
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Adding LUN's or datastores in VMware
We are using VMware 5.0 and I have been tasked with trying to add multiple LUN's from our EMC San to the one Redhat 6.5 VM. I have not found any documentation about using multiple LUN's from a SAN to one VM. Is this even possible? Is it possible to add multiple datastores to one VM. Usually we have just one LUN for VM or one large LUN with Multiple VM's, but not the other away around.
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Hi,
just to talk about the vocabulary :
- a LUN is a logical disk unit on a San
- a Datastore is logical disk unit on ESX, it can be a whole LUN, or part of it
- a VMDK is a VM's virtual disk, stored on a datastore ; so again it is a logical disk unit, but the last layer one
So you can't "add datastores" to a VM, you add VMDK or RDM to it.
But you can add multiple VMDK to a VM, and these VMDK can belong to different LUN on your San.
RDM is a way to present a LUN directly to your VM, for the VM to "speak" directly to the San as if you presented a LUN to a physical server, so there is no VMDK in this case.
just to talk about the vocabulary :
- a LUN is a logical disk unit on a San
- a Datastore is logical disk unit on ESX, it can be a whole LUN, or part of it
- a VMDK is a VM's virtual disk, stored on a datastore ; so again it is a logical disk unit, but the last layer one
So you can't "add datastores" to a VM, you add VMDK or RDM to it.
But you can add multiple VMDK to a VM, and these VMDK can belong to different LUN on your San.
RDM is a way to present a LUN directly to your VM, for the VM to "speak" directly to the San as if you presented a LUN to a physical server, so there is no VMDK in this case.
do you require more assistance with this question, to be able to close out.
Depends what you want to do, present a RAW LUN, e.g. RAW Device Mapped direct LUN to SAN to VM, and format it with native file system.
or present multiple LUNs to ESXi, create datastores, and then create virtual machine disks for your VMs, on different datastores.
RDMs/RAW LUNs, are not often used these days, unless special circumstances exist like Clustering.
VMDKs are easier to manage, and perform just as well now!
see this link
https://www.vmadmin.co.uk/resources/35-esxserver/58-rdmvm
also see this
RDM versus VMDK performance
Conclusion: VMFS and RDM have similar performance. Don’t choose RDM for performance.
Source:http://www.vfrank.org/2011/03/22/performance-rdm-vs-vmfs/