Storage pool disappeared from guest, appeared on host after reboot

Mike-2930 61 Reputation points
2022-09-29T15:12:28.893+00:00

Two physical disks were set as Offline in Disk Management on the Hyper-V host, and then they were mounted and set up as a mirror storage pool in the guest. Everything seemed to work well, also across reboots of both host and guest. Host and guest are Windows Server 2022, file system is ReFS (auto-healing feature is desired).

Following a power loss, the two disks were "captured" by the host on reboot. They no longer show as Offline (they are not even visible in Disk Management), and thus are "Physical drive Not found" by the virtual machine. The disks are listed (but not mounted) with a yellow triangle under Storage Pools on the host, ready to be read-write enabled and used there.

The question is: how can the two disks again be made available to the Hyper-V guest? Here are some related unanswered Technet Forum questions from 2012-2014:

Is it at all supported to have a pool set up in the guest, and what are the best practices for doing this? Our setup obviously had a weakness in this respect. At the same time, the issue is known at least since 2014 (that post too mentions everything working until there was a power loss, which defies the purpose of "resiliency").

I've been thinking about alternatives like managing the storage pool on the host, and mounting the resulting virtual disk (offline on host) on the guest, as well as using the pool and virtual disk on the host to store a VHDX file to be mounted on the guest, however these do not seem to deliver the same "bitrot healing" benefits to the guest that mirroring+ReFS would deliver if handled in combination on the guest itself, which is a goal. In the first case, I suppose that the guest doesn't know that the volume is a storage pool on the host (thus mirror can't be used for ReFS healing), and in the second case, as documented, the entire VHDX file would be deleted if corruption is detected, but healing fails (not to mention the fact that integrity streams are not supported for VHDX files). One of the commenters in the above went as far as implementing a mirrored storage space in the guest by using a pair of VHDX files, but his question too did not receive an answer.

It seems to me that a lot of great work went into integrating ReFS and Storage Pool capabilities, but 10+ years later we are still missing a supported mechanism for VM guests to benefit from the same "self healing" capabilities, via ReFS-formatted VHDX stored on a ReFS virtual disk, or otherwise.

Hyper-V
Hyper-V
A Windows technology providing a hypervisor-based virtualization solution enabling customers to consolidate workloads onto a single server.
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Windows Server Storage
Windows Server Storage
Windows Server: A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.Storage: The hardware and software system used to retain data for subsequent retrieval.
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  1. Courtney Renegar 20 Reputation points
    2023-11-15T16:59:31.0533333+00:00

    Exact same issue here but mine had no power loss. After a clean shutdown, it was rebooted at the customer site and the VM would not start until the two physical drives were removed. The storage pool was not listed at all on the VM and had to be forcibly removed using PS to get the 2 physical dives to reappear on the host. They were visible in Device Manager but not Computer Management. It does seem strange that a best practice for this implementation still does not exist.

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