Copy Services considerations for VMware ESXi/ESX hosts

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Review considerations for using the Copy Services functions with a VMware ESXi/ESX server.

Copy Services are only available for individual LUNs.
The DS8000® does not recognize Virtual Machine File Server (VMFS) volumes or extents so you must copy all LUNs that might be contained within a VMFS volume. To prevent LUN locking problems, no virtual machine can use a copy target volume during the copy process.
The source and target volumes must be on separate physical machines
The VMFS file system uses a label mechanism and if it encounters two volumes with the same label, only one remains accessible.
Remote Mirror and Copy read from secondary option is not supported
“Read from secondary” allows a target volume to be opened in read-only mode during a Remote Mirror and Copy operation. VMware ESX Server does not open volumes in read-only mode and therefore is not able to access a Remote Mirror and Copy target while a copy is in progress.
Rescan of LUNS might be required
VMFS is able to discover changes on a hard disk drive at the file system level. It can manage a copy if the system knows that there is a VMFS file system to discover:
  • If the copy target volume was discovered at system start time without a VMFS file system, you must rescan for the changes.
  • If there is a VMFS file system, the server can use the new information immediately without any intervention.
Additional considerations
Copy Services functions are supported for any DS8000 LUN that is attached to an ESX server, with the following important restrictions and recommendations:
  • The copy relationship must not be persistent if the target LUNs are used with a VMware host. If you are using the Metro Mirror function, the complete relationship must be severed; if the suspend or read-only options are used, VMware cannot use the copied LUNs.
  • If the target LUNs are used within the same VMware Datacenter as the source LUNs, a resignature operation is required (see the VMware SAN Configuration Manual, which is available at VMware).
  • Ensure that you create separate DS8000 volume groups for the set of source LUNs and the sets of target LUNs. The LUNs in the target volume group must have the same order and size as LUNs in the source volume group. Only one set of target LUNs can be presented to a single VMware host.
  • Ensure that LUN names are distinctive for each type or set of copy operations. Distinctive names aid in postoperation identification of LUNs.
  • Raw device mapping (RDM) LUNs might require reattachment to the OS image that was copied. The OS image must be edited so that the existing RDM LUNs are removed, and then add the appropriate LUNs. Data is preserved during this operation.
  • If an OS image is running during a copy operation, there might be a loss of data that is caused by the timing of I/O buffer flushes. For absolute data integrity, shut down the guest OS image during the copy operation.