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ERROR_SVHDX_UNIT_ATTENTION_CAPACITY_DATA_CHANGED
New functionality of the Hyper-V 4.0 hypervisor in the field of high availability of services - shared VHDX files or Shared VHDX. With Shared VHDX technology, multiple virtual machines can share one shared VHDX format VHD at the same time. Thus, it became possible to organize guest clusters (based only on virtual machines) without the need to use iSCSI or FC inside virtual machines.
Note: Recall that earlier it was possible to build guest clusters based on Hyper-V, however, this scenario assumed the need to connect a virtual machine to storage via iSCSI and Virtual Fiber Channel (which appeared in Windows Server 2012 and provides the ability to connect a virtual machine through a virtual HBA module directly to storage FC). Thus, the virtual machine was given direct access to the storage, which is especially inconvenient for hosting providers and providers of other cloud solutions.
General VHDX allows you to abstract from the implementation of the storage system, hiding from the VM administrator on which particular disk array and LUN its files are located.
Using Shared VHDX disks retains the ability to use all the "features" of Hyper-V: Live Migration, Storage Live Migration and Dynamic Memory.
Possible Shared VHDX Configurations
Shared VHDX disks in Windows Server 2012 R2 can be used in two different configurations:
- Shared VHDX on a clustered CSV. Shared VHDX disk files reside on the CSV volume of the physical cluster. A Cluster Shared Volume can be set up on any file storage that is supported by the Windows Clustering Service: iSCSI, FC, or Shared SAS
- Shared VHDX in a file cluster share. Shared VHDX disks are located on a network directory located on a Scale-Out File Server file cluster. Note that the Scale-Out File Server cluster itself also requires a CSV volume.
High availability of shared VHDX disks in both cases is implemented through host clustering; a guest cluster created on the basis of these disks ensures high availability of applications and services inside virtual machines.