Known issues and limitations with Microsoft Hyper-V hosts

Ensure that you are familiar with the Microsoft Hyper-V host attachment requirements to verify and troubleshoot your configuration.

To enable the copy offload function, you must have IBM subsystem device driver device-specific module (SDDDSM) version 2450 or later installed. ODX is disabled by default so that you can install the correct version of SDDDSM. After the correct SDDDSM version is installed, you enable ODX by entering the chsystem -odx on CLI command.

Although Microsoft ODX is supported, there is a limitation from the Windows side for supporting ODX online. The volumes that are mapped to the host are not ODX capable in Windows until they are unmapped and then mapped again.

To unmap and map the volumes, follow these steps:
  1. Bring down the applications by using the volumes so that the applications stop using the volumes.
  2. Disconnect or logout the host from the storage.
  3. Rediscover the volumes from the Server Manager (the volumes go away).
  4. Reconnect or log in the host to the storage.
  5. Rediscover the volumes from the Server Manager (the disks reappear).
  6. Start the applications.
Note: If these LUNs are formatted with an allocation unit size that is less than 4 KB, ODX might not work on these LUNs. A subpage-aligned I/O (less than 4 KB) is not allowed.

You can add new LUNs to a Windows host for consumption of an ODX-aware application. The system array works best with ODX when LUNs that are exported to the Windows host are formatted with 32 KB NTFS cluster size. Therefore, ensure that the allocation unit size for the New Technology File System (NTFS) is greater than or equal to 32 KB. The default on the Windows Server 2012 release 2 is 4 KB, which might not result in the performance that the system can deliver.