Need clearification on FT requirement

[TapeshGoyal]

Hi,

Required  Storage: Ensure that the datastore is not using physical RDM (Raw Disk Mapping). Virtual RDM is supported.

which datastore is it talking about ? Does it talking about datastore where VM is installed?

Does FT works if I have one VM that is having physical RDM, and RDM is stored in another shared datastore where VM is not installed.

Any answers on this will be appreciated.

Thanks,

Tapesh.

[Texiwill · Accepted solution]

Hello,

Required  Storage: Ensure that the datastore is not using physical RDM (Raw Disk Mapping). Virtual RDM is supported.

which datastore is it talking about ? Does it talking about datastore where VM is installed?

Yes. The same Data Store must be seen by BOTH hosts involved in FT.

Does FT works if I have one VM that is having physical RDM, and RDM is stored in another shared datastore where VM is not installed.

Physical RDM is NOT supported, only Virtual RDM.

Best regards, Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009, DABCC Analyst[/url]
Now Available on Rough-Cuts: 'VMware vSphere(TM) and Virtual Infrastructure Security: Securing ESX and the Virtual Environment'[/url]
Also available 'VMWare ESX Server in the Enterprise'[/url]
[url=http://www.astroarch.com/wiki/index.php/Blog_Roll]SearchVMware Pro[/url]|Blue Gears[/url]|Top Virtualization Security Links[/url]|Virtualization Security Round Table Podcast[/url]

[MattG]

I could be reading this wrong, but I get the impression that you are asking if FT can replicate from a VM on an RDM to a VM on a VMFS volume?

FT does not replicate. It is a failover mechanism like MSCS that will failover a running VM to another standby VM. Just like MSCS they use the same exact files on the shared storage. FT does not replicate the storage.

-MattG

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[TapeshGoyal]

Thanks for reply, one extended question

When FT uses VMotion as underlying technology, why FT doesn't support Physical RDM, while VMotion support it ?

Thanks,

Tapesh.

[MattG]

FT uses vLockstep as the underlying technology. It does not use vMotion.

-MattG

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[Texiwill]

Hello,

FT uses vLockstep as the underlying technology. It does not use vMotion.

Actually it uses both. FT when initialized will create a shadow VM that has the same disk source, then use VMotion, or something similar, to transfer the current IN USE memory. Once that is done, vLockStep is enabled and the VMs are running the same code.

To share the same disk source as FT does it needs to do some locking that only VMDK and Virtual RDMs allow. Physical RDMs can not participate in this same locking mechanism.

Best regards, Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009, DABCC Analyst[/url]
Now Available on Rough-Cuts: 'VMware vSphere(TM) and Virtual Infrastructure Security: Securing ESX and the Virtual Environment'[/url]
Also available 'VMWare ESX Server in the Enterprise'[/url]
[url=http://www.astroarch.com/wiki/index.php/Blog_Roll]SearchVMware Pro[/url]|Blue Gears[/url]|Top Virtualization Security Links[/url]|Virtualization Security Round Table Podcast[/url]

[danielbrookes]

Hello TexiWill,

Do you know if this will change any time soon or is it just plain simple not possible?

To share the same disk source as FT does it needs to do some locking that only VMDK and Virtual RDMs allow. Physical RDMs can not participate in this same locking mechanism.

We have a whole bunch of VM's which have RDM's mapped but they are configured as Physical rather than Virtual. I need to do some testing before we commit to changing them all to Virtual but I may be wasting my time if its due to change.

[Gleed]

I can tell you it won't change in the next release. Can't say beyond that...

-Kyle