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VMotion and Delphix Frequently Asked Questions (KBA1391)



Q:Can a Delphix Engine VM be vMotioned to a new ESX host without being shut down?

Yes, subject to these considerations:

Live vMotion of a Delphix Engine VM is supported, but one must consider two factors: the load on the Delphix Engine at the time of the vMotion, and the bandwidth available on the vMotion network.

When a VM is vMotioned while running, ESX needs to copy every page of memory of the VM from one ESX host to another across the vMotion network. As the copy is in progress, pages are changing, and the changes need to be copied as well.

Delphix Engines usually have a large amount of memory and a significant rate of change of memory when VDBs are in use. For this reason it is recommended that the vMotion network be at least a 10Gb, dedicated network between the ESX hosts in order to perform a live vMotion of a Delphix Engine.

Q: Does Delphix support DRM for Delphix Engine VMs?

Yes, subject to these considerations:

Dynamic Resource Management, or DRM, VMWare's technology for distributing VM load across a cluster of ESX servers, relies on live vMotion of VMs in the cluster. See the previous FAQ for information on live vMotion of a Delphix Engine VM. 

Delphix recommends as the ideal configuration an ESX host dedicated to the Delphix Engine VM, which configuration precludes that ESX host participating in DRM.

If this is not possible, Delphix recommends that memory and CPU resources allocated to the Delphix Engine VM be fully reserved for the Delphix Engine VM. This would preclude DRM migrating VMs in a way that overcommits resources needed by the Delphix Engine VM. 

If neither of these recommendations can be adhered to, DRM can lead to severe performance degradation of a Delphix Engine VM, and would not be supported.

Q: Does a vMotion of a Delphix Engine VM or target server VM affect client access to VDBs?

Not noticeably. A vMotion results in an interruption of a fraction of a second to a few seconds in network connectivity to the VM, depending on network infrastructure. The higher-level protocols involved in use of a VDB, such as NFS and JDBC/ODBC, are resilient to brief interruptions.