how to determine RDM mode for requirment

[biohazard4]

Hi,

I have following questions about physical RDM and virtual mode.

1. If the requirment ask the san-aware applications to be used inside VM, that means we must set the virtual disk as physical mode, can't set as virtual mode, right? If so, that means this VM can't be cloned or snapshotted and covert to template, right?

2. If set the virtual mode, that means the VM only can access the storage space, but can't use the san-related software. is that correct?

[binoche · Accepted solution]

when RDM in virtual mode, not only san-aware applications but also esx features such as snapshot can be used

binoche, VMware VCP, Cisco CCNA

[AndreTheGiant]

It depens on which features do you require and how them are working.

For example, for iSCSI you can use a guest initiator inside the VM and usually all is working fine.

For FC, on a EMC Clariion, you can send command using the management interface, so snap, clone, mirror can work also in virtual mode.

Andre

[AlbertWT]

Yes Bio, the only reason why people using physical comaptibility mode is just for Microsoft Clustering Services or something else.

I myself prefer RDM with Virtual Compatibility mode.

Kind Regards,

AWT

[biohazard4]

Binoche, do you mean in vSphere, the virtual RDM can also be used for san-aware application? But in VI3, only physical RDM supports the san-aware applicaiton.

[binoche]

sorry, but san-aware applicaitons provided by storage array vendors, they should be able to use always, right?

[PDF here] Raw Device Mapping

binoche, VMware VCP, Cisco CCNA

[biohazard4]

Andre, do you mean the ESX box use the HW iSCSI adpater? since the SW-iSCSI can't create the RDM virtual disk

[AndreTheGiant]

since the SW-iSCSI can't create the RDM virtual disk

Is possible... not so used... but it is possible.

Andre

[biohazard4]

Andre, yes, you're right. I did experiment the SW-iSCSI can create RDM both virtual and physical.