Enterprise Virtualization Recovery

Microsoft Hyper-V Data Recovery

We recover VHD/VHDX virtual disks from failed RAID arrays, repair broken checkpoint chains, reconstruct Cluster Shared Volumes, and extract VMs from corrupted Hyper-V hosts. Free evaluation. No data = no charge.

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How Hyper-V Environments Fail and How We Recover Them

Microsoft Hyper-V stores virtual machines as VHD or VHDX files on NTFS or ReFS volumes, often backed by RAID arrays or SAN LUNs. When the underlying storage fails, the Hyper-V host loses access to the virtual disks and all VMs on that volume go offline. Recovery requires imaging the physical drives, reconstructing the RAID array (if applicable), parsing the host filesystem, and extracting each .vhdx file individually.

VHDX replaced VHD in Windows Server 2012 as the default virtual disk format. It supports up to 64TB per file, uses a 4KB log-based metadata structure for crash consistency, and can be either fixed-size or dynamically expanding. Checkpoints (formerly "snapshots") create .avhdx differencing disks that track block-level changes relative to a parent. Cluster Shared Volumes (CSV) extend the storage model to failover clusters, allowing multiple Hyper-V hosts to access the same LUN simultaneously.

VHDX On-Disk Structure and Failure Points

Understanding the VHDX binary layout is required for targeted recovery. The format was designed for resilience, but storage-layer failures can still render files unreadable.

VHDX Header and Metadata

File identifier at offset 0 (64KB VHDX signature), followed by two header copies at offsets 64KB and 128KB for redundancy
Region table at offset 192KB describes the location of the BAT (Block Allocation Table) and metadata regions within the file
BAT maps each virtual disk block to its physical offset in the VHDX file; for dynamic disks, unallocated blocks have a BAT entry of zero
4KB log region between the headers records pending metadata updates; Hyper-V replays this log on mount to ensure consistency
Metadata region stores virtual disk size, logical/physical sector size, and parent locator (for differencing disks)

Differencing Disks (.avhdx)

Each checkpoint creates an .avhdx file that becomes the active write target; the parent .vhdx becomes read-only
.avhdx files use the same VHDX format but with a parent locator in the metadata region pointing to the parent file by path and unique ID
Block-level change tracking: only modified blocks have BAT entries; reads for unmodified blocks are passed through to the parent
Merge operation (checkpoint deletion) copies changed blocks from the .avhdx into the parent; power loss during merge can leave both files in an inconsistent state
Deep checkpoint chains (5+ levels) increase fragmentation and I/O latency; failed merges at any level can strand the entire chain

When a RAID failure corrupts the NTFS volume hosting the VHDX files, the Hyper-V host cannot read the VHDX headers, BAT, or log region. Standard Hyper-V tools (Inspect-VHDXDisk, Merge-VHD) require a mounted volume. Our approach bypasses the host entirely: we parse VHDX structures from the raw RAID image and extract virtual disks by following BAT entries.

Cluster Shared Volume Recovery

Cluster Shared Volumes allow multiple Hyper-V hosts in a Windows failover cluster to access the same NTFS volume simultaneously. CSV coordinates access through a metadata layer that assigns ownership of individual VHDX files to specific cluster nodes. When the underlying storage fails, the CSV layer is irrelevant; recovery targets the NTFS filesystem and VHDX files directly.

NTFS underneath: CSV uses standard NTFS on the SAN LUN or RAID volume. The cluster coordination layer (CSV metadata) controls which node has direct I/O access to which files, but the actual file storage is plain NTFS. Once we have the raw RAID image, we parse NTFS normally.
ReFS on Server 2016+: Windows Server 2016 and later support ReFS for CSV volumes. ReFS uses a B+ tree structure for metadata and allocator-based storage for data. Our tooling handles both NTFS and ReFS volume parsing from raw images.
Redirected I/O fallback: When a CSV owner node loses direct SAN access, other nodes fall back to redirected I/O over the cluster network. If multiple nodes lose storage access simultaneously, all VMs on the CSV go offline. The data is still on the physical drives; the CSV coordination failure is a software problem, not a storage problem.

Hyper-V Replica Failure Scenarios

Hyper-V Replica asynchronously replicates VM changes to a secondary host. Replica is not a backup; it creates a point-in-time copy that can diverge from the primary if replication falls behind. When both the primary and replica sites experience storage failures, we recover from whichever site has the most recent consistent data.

Primary Site Failure

Primary host RAID fails. Replica site has a copy that is up to the last replication cycle (default: 5 minutes). We recover from the replica VHDX files, which may be missing the most recent 5 minutes of writes.

Both Sites Failed

Both primary and replica storage failed (ransomware, site-wide power event, or cascading RAID failures). We image drives from both sites and compare the VHDX timestamps to determine which copy has the most recent consistent data. Partial recovery from both copies may yield a more complete dataset.

Recovery Methodology for IT Administrators

Step-by-step procedures for Hyper-V environment recovery. If you are evaluating our technical capability, this is how the work gets done.

1. Storage Layer Imaging

Each physical drive is imaged through PC-3000 using SAS HBAs for SAS drives or SATA/NVMe adapters as appropriate. For drives with bad sectors, we configure head maps to skip damaged heads on initial passes and revisit them with aggressive retry parameters after all healthy data is captured. DeepSpar Disk Imager provides hardware-level timeout control for drives that lock up mid-read.

2. RAID Reconstruction

If the Hyper-V host uses a hardware RAID controller (PERC, Smart Array, MegaRAID), we read the controller metadata from each drive image using PC-3000 RAID Edition. This gives us stripe size, member ordering, parity rotation, and RAID level without needing the original controller hardware. For Storage Spaces Direct (S2D) or software RAID, we parse the Windows Storage Spaces metadata from the drive images.

3. NTFS/ReFS Parsing and VHDX Extraction

With the RAID image reconstructed, we parse the NTFS or ReFS volume to locate .vhdx, .avhdx, .vmcx (VM configuration), and .vmrs (runtime state) files. Each VHDX is extracted by reading its BAT and following the block offsets to their physical locations in the volume. For dynamically expanding disks, only allocated blocks are present in the file.

4. Checkpoint Consolidation

If the VM has checkpoints, we reconstruct the .avhdx chain by reading each differencing disk's parent locator metadata. Changed blocks from each .avhdx are applied in sequence to the base .vhdx. If a merge was in progress when the failure occurred, we determine the merge progress from the BAT state and complete the consolidation manually. The output is a single flat VHDX representing the VM at its most recent consistent state.

Hyper-V Recovery Pricing

Hyper-V recovery follows the same transparent pricing model as every other service: per-drive imaging based on each drive's condition, plus a $400-$800 reconstruction fee that includes RAID rebuild, NTFS/ReFS parsing, and VHDX extraction. No data recovered means no charge.

Service Tier	Price Range (Per Drive)	Description
Logical / Firmware Imaging	$250-$900	Firmware module damage, SMART threshold failures, or filesystem corruption on individual array members.
Mechanical (Head Swap / Motor)	$1,200-$1,50050% deposit	Donor parts consumed during transplant. SAS drives require SAS-specific donors matched by model, firmware revision, and head count.
Reconstruction + VHDX Extraction	$400-$800per array	RAID reconstruction, NTFS/ReFS parsing, VHDX extraction, and checkpoint chain consolidation if applicable.

No Data = No Charge: If we recover nothing from your Hyper-V environment, you owe $0. Free evaluation, no obligation.

Enterprise competitors charge $5,000-$15,000 with opaque "emergency" surcharges. We publish our pricing because the work is the same regardless of what label gets put on the invoice.

Hyper-V Recovery; Common Questions

What causes VHDX file corruption and can it be recovered?

VHDX files use a 4KB log structure for crash consistency. Power loss during a metadata commit can leave an incomplete log entry. If the log replay fails on Hyper-V startup, the VHDX becomes unmountable. Recovery involves parsing the VHDX header, BAT (Block Allocation Table), and log entries from the raw disk image, then reconstructing a consistent virtual disk from the committed log entries.

How do you recover data from a failed Cluster Shared Volume?

Cluster Shared Volumes (CSV) use NTFS on the underlying storage with a coordination layer across Windows failover cluster nodes. When the underlying RAID array or SAN LUN fails, the CSV goes offline and all VMs on that volume are stopped. Recovery does not depend on the cluster coordination metadata. We image the underlying physical drives, reconstruct the RAID array, parse the NTFS filesystem, and extract the .vhdx files for each VM.

Can you fix a broken Hyper-V checkpoint chain?

Yes. Hyper-V checkpoints create .avhdx (Auto VHDX) differencing disks. Each .avhdx contains a BAT (Block Allocation Table) mapping changed blocks relative to its parent. When a checkpoint merge fails or the chain references are corrupted, the VM cannot start. We read the BAT from each .avhdx, determine correct parent-child ordering, and manually consolidate the differencing blocks back into the base .vhdx.

My Hyper-V failed to merge a differencing disk. Can you complete the merge?

Yes. A failed merge leaves orphaned .avhdx files that Hyper-V no longer tracks in the VM configuration (.vmcx). We parse each differencing disk's Block Allocation Table to identify which sectors it owns, then merge them in creation-time sequence into the base VHDX. The result is a single consolidated virtual disk at the VM's most recent consistent state.