Limitations to Protection and Recovery of Virtual Machines in SRM

The protection and recovery by Site Recovery Manager of virtual machines is subject to limitations.

Protection and Recovery of Suspended Virtual Machines

When you suspend a virtual machine, vSphere creates and saves its memory state. When the virtual machine resumes, vSphere restores the saved memory state to allow the virtual machine to continue without any disruption to the applications and guest operating systems that it is running.

Protection and Recovery of Virtual Machines with Snapshots

Array-based replication supports the protection and recovery of virtual machines with snapshots, but with limitations.

You can specify a custom location for storing snapshot delta files by setting the workingDir parameter in VMX files. Site Recovery Manager does not support the use of the workingDir parameter.

Limitations also apply if you are running versions of ESX or ESXi Server older than version 4.1.

■	If the virtual machine has multiple VMDK disk files, all the disk files must be contained in the same folder as the VMX file itself.
■	If a virtual machine is attached to a Raw Disk Mapping (RDM) disk device, you must store the mapping file in the same folder as the VMX file. RDM snapshots are only available if you create the RDM mapping using Virtual Compatibility Mode.

If you are running a ESX or ESXi Server 4.1 or later, these limitations do not apply.

vSphere Replication supports the protection of virtual machines with snapshots, but you can only recover the latest snapshot. vSphere Replication erases the snapshot information in the recovered virtual machine. As a consequence, snapshots are no longer available after recovery, unless you configure vSphere Replication to retain multiple point-in-time snapshots. For information about recovering older snapshots by using multiple point-in-time snapshots with vSphere Replication, see Replicating a Virtual Machine and Enabling Multiple Point in Time Instances.

Protection and Recovery of Virtual Machines with Memory State Snapshots

When protecting virtual machines with memory state snapshots, the ESXi hosts at the protection and recovery sites must have compatible CPUs, as defined in the VMware knowledge base articles VMotion CPU Compatibility Requirements for Intel Processors and VMotion CPU Compatibility Requirements for AMD Processors. The hosts must also have the same BIOS features enabled. If the BIOS configurations of the servers do not match, they show a compatibility error message even if they are otherwise identical. The two most common features to check are Non-Execute Memory Protection (NX / XD) and Virtualization Technology (VT / AMD-V).

Protection and Recovery of Linked Clone Virtual Machines

vSphere Replication does not support the protection and recovery of virtual machines that are linked clones.

Array-based replication supports the protection and recovery of virtual machines that are linked clones if all the nodes in the snapshot tree are replicated.

Protection and Recovery of Virtual Machines with Reservations, Affinity Rules, or Limits

When Site Recovery Manager recovers a virtual machine to the recovery site, it does not preserve any reservations, affinity rules, or limits that you have placed on the virtual machine. Site Recovery Manager does not preserve reservations, affinity rules, and limits on the recovery site because the recovery site might have different resource requirements to the protected site.

You can set reservations, affinity rules, and limits for recovered virtual machines by configuring reservations and limits on the resource pools on the recovery site and setting up the resource pool mapping accordingly. Alternatively, you can set reservations, affinity rules, or limits manually on the placeholder virtual machines on the recovery site.

Protection and Recovery of Virtual Machines with Components on Multiple Arrays

Array-based replication in Site Recovery Manager depends on the concept of an array pair. Site Recovery Manager defines groups of datastores that it recovers as units. As a consequence, limitations apply to how you can store the components of virutal machines that you protect using array-based replication.

■	Site Recovery Manager does not support storing virtual machine components on multiple arrays on the protected site that replicate to a single array on the recovery site.
■	Site Recovery Manager does not support storing virtual machine components on multiple arrays on the protected site that replicate to mulitple arrays on the recovery site, if the virtual machine components span both arrrays.

If you replicate virtual machine components from multiple arrays to a single array or to a span of arrays on the recovery site, the VMX configurations of the UUID of the datastores on the protected site do not match the configurations on the recovery site.

The location of the VMX file of a virtual machine determines which array pair a virtual machine belongs to. A virtual machine cannot belong to two array pairs, so if it has more than one disk and if one of those disks is in an array that is not part of the array pair to which the virtual machine belongs, Site Recovery Managercannot protect the whole virtual machine. Site Recovery Manager handles the disk that is not on the same array pair as the virtual machine as an unreplicated device.

As a consequence, store all the virtual disks, swap files, RDM devices, and the working directory for the virtual machine on LUNs in the same array so that Site Recovery Manager can protect all the components of the virtual machine.