Every VMware to Nutanix AHV migration project comes with the same fundamental tension: you want to move workloads to a better platform without disrupting the people who depend on those workloads every day. The good news is that Nutanix Move, when paired with a well defined phased methodology, handles that tension well. This post walks through how we approach these engagements at ePlus, covering the migration mechanics, database specific considerations, and the operational steps that close out each phase cleanly.
How Nutanix Move Works
Nutanix Move is a cross hypervisor mobility tool that automates VM migrations from VMware ESXi, Hyper-V, or public cloud sources to Nutanix AHV. The core model is straightforward: Seed, Sync, Cutover.
- Discovery: Connect Move to the source environment (vCenter, standalone ESXi, or Hyper-V) and the target Nutanix cluster. Move inventories the VMs and validates compatibility before anything touches production data.
- Data Seeding: Move creates a placeholder VM on the AHV side and begins copying virtual disks from the source. This initial seed runs in the background while the source VM stays live.
- Changed Block Tracking (CBT): After the initial copy, Move uses CBT to replicate only blocks that have changed since the last sync. This keeps the replication delta small and the eventual cutover window short.
Why Daytime Replication Is Safe
A common concern when planning migrations is whether running replication during business hours will hurt production performance. In practice, it does not, and here is why.
| Non Disruptive Snapshots Move uses native snapshot mechanisms (VMware CBT, for example) to read source data. The VM stays powered on and users experience no interruption. | Network Throttling Move supports bandwidth throttling on migration traffic so replication does not compete with production traffic on shared links during peak hours. |
| Background Operation The seeding phase is a background task. End users are fully isolated from the process because their application is still running on the source hypervisor. | Incremental Efficiency After the initial seed, subsequent syncs only move changed blocks, so the bandwidth consumption of ongoing replication is a fraction of the initial transfer. |
The Cutover Process
The cutover is the only step that involves any downtime, and even that window is typically measured in minutes per VM. The sequence is deterministic and should be documented in the project plan before any work begins.
- Final Sync: Move performs one last incremental sync to capture the most recent changed blocks.
- Graceful Shutdown: The source VM is powered off cleanly, not forcefully terminated.
- Final Delta: A final incremental pass captures any blocks written during the shutdown sequence.
- Activation: Move installs the required VirtIO drivers for AHV, optionally reconfigures IP addressing, and powers the VM on within the Nutanix cluster.
Practical Note
For most general purpose VMs, the combined downtime from final sync through power on on AHV is under five minutes. Database VMs with large in flight transactions may take slightly longer depending on the final delta size.
Rollback Strategy
One of the most important things to communicate to stakeholders before a cutover is that rollback is not a complex recovery procedure. It is simply reversing a power state.
Because Move does not delete or modify the source VM during cutover (it only powers it off and disconnects its network interface), the path back to the original state requires no data restoration. If a migrated VM does not perform as expected on AHV, the steps are:
- Power off the VM on the Nutanix AHV side.
- Reconnect the network interface on the source VM.
- Power on the source VM in the original environment.
The source disks remain completely untouched throughout the process, so this rollback takes seconds rather than hours. It also means stakeholder sign off on a cutover carries much lower risk than it would in a traditional migration approach.
Special Migration Scenarios
Not every VM is a candidate for a straightforward Move migration. A few categories require a different approach:
- Legacy Operating Systems: Windows Server 2003 and older Linux kernels with unsupported kernel versions are explicitly unsupported by modern versions of Nutanix Move and the standard AHV VirtIO driver set. These workloads cannot use the standard Move migration path and require an alternative approach such as a cold clone, a bare metal backup restoration, or an application level migration to a newly provisioned VM.
- Physical Hardware Pass through: VMs with PCI pass through devices or Raw Device Mappings (RDMs) require manual reconfiguration on the target side.
- Shared Disk Clustering: Certain older Oracle RAC or MSCS configurations that rely on shared SCSI bus emulation need architectural review before migration.
For these cases, the alternatives range from a manual cold clone, to an application level migration, to a fresh OS installation with data restoration from backup. The right path depends on the workload, and that decision should be made during technical discovery before the project schedule is finalized.
Database Migration Methodology
Databases deserve a separate treatment because the consequences of a failed migration, or even a migration that succeeds but lands on a poorly configured target, are higher than for stateless application servers. We cover both Microsoft SQL Server and Oracle here.
Storage Architecture for Database VMs
Nutanix gives database workloads two primary storage paths: native vDisks and Nutanix Volume Groups.
- Native vDisks are the default for AHV VMs and are simple to manage through Prism. Starting with AOS 6.x, the Autonomous Extent Store (AES) improved local sharding for native vDisks, so they are no longer as constrained as they were in earlier releases. That said, a single CVM still serves as the primary I/O path for a given vDisk, which means very high throughput workloads can reach a performance ceiling at the CVM level.
- Nutanix Volume Groups (VG) are collections of vDisks presented as block devices. For AHV, VGs can be direct attached, appearing as native SCSI devices to the guest OS. When Volume Group Load Balancing (VGLB) is enabled, the system shards vDisks across all CVMs, removing the single CVM I/O path and allowing the database to draw on the aggregate throughput of the entire cluster’s Stargate processes.
iSER Support: For the highest performance requirements, Nutanix supports iSER (iSCSI Extensions for RDMA), which bypasses the TCP/IP stack entirely to reduce latency and CPU overhead between the guest and the CVM. This is worth evaluating for latency sensitive OLTP workloads.
AHV Specific Tuning for Databases
Several AHV configuration decisions have a direct and measurable impact on database performance.
- vCPU to pCPU Ratio: For production databases, size assuming 1 vCPU equals 1 physical core, not one hyperthreaded thread. Oversubscription introduces CPU Ready Time, which is particularly harmful to latency sensitive query workloads. Target below 5% CPU Ready.
- Memory Reservations: Reserve 100% of assigned VM memory for SQL Server and Oracle VMs. AHV memory reclamation through ballooning or swapping can cause significant and hard to diagnose latency spikes in database workloads.
- Huge Pages: AHV uses 2 MB Huge Pages to reduce Translation Lookaside Buffer (TLB) pressure. Ensure the guest OS is configured to use large page allocations to take advantage of this.
- vNUMA: For VMs larger than a single physical socket, enable vNUMA and match the virtual topology to the physical hardware. This allows the database engine to schedule threads and memory access with NUMA awareness. Disable CPU hot add, as enabling it disables vNUMA and can cause performance degradation of up to 30%.
AOS Features That Matter for Databases
| Data Locality AOS stores a VM’s data on the same physical node where the VM runs. Read I/O is served locally without network traversal, which reduces database read latency materially. | AHV Turbo (Frodo I/O Path) Bypasses traditional QEMU emulation with a multi-queue I/O path that scales with the number of vCPUs, delivering higher I/O capacity and lower CPU overhead for storage intensive workloads. |
| Nutanix Blockstore A block management system that moves device interactions into user space, eliminating context switching and kernel driver overhead for data disks. | VGLB for OLAP Volume Group Load Balancing distributes I/O across all CVMs in the cluster. Critical for high throughput OLAP and reporting workloads that can saturate a single CVM. |
Microsoft SQL Server Migration Options
There are three viable paths for SQL Server migrations, and the right choice depends on the deployment type and the acceptable downtime window.
- Nutanix Move: The simplest path for standalone instances. Move handles disk conversion to AHV RAW format, VirtIO driver injection, and IP configuration. Best suited for standalone instances where a brief cutover window is acceptable.
- Always On Availability Groups: Build a new SQL VM on AHV, join it to the existing Windows Server Failover Cluster (WSFC), and add it as a new secondary AG replica. Once synchronized, perform a planned manual failover to promote the Nutanix based node, then decommission the old nodes. This approach reduces cutover risk for business critical SQL workloads and can achieve near zero application downtime.
- Backup and Restore: Take a full backup of the source database, restore it on a pre staged SQL VM on AHV using
WITH NORECOVERY, and during the cutover window take a tail log backup, restore it withWITH RECOVERY, and redirect applications to the new instance.
Oracle Migration Options
- Nutanix Move: Recommended for migrating the Oracle VM as is from vSphere to AHV when the VM itself is in Move’s compatibility matrix. Move handles VirtIO driver injection automatically.
- RMAN Active Duplication: Use Oracle Recovery Manager to perform an active duplication from the source to a new Oracle VM on AHV. The source database remains online until the final switchover, minimizing the downtime window.
- Data Guard: Set up a physical standby on the Nutanix cluster, synchronize it via RMAN, and then perform a Data Guard switchover to promote the Nutanix instance to primary. This is the lowest risk option for Oracle databases with strict RPO/RTO requirements.
- Oracle RAC with Nutanix Volumes: For RAC deployments, Nutanix Volumes provide the shared block storage required by clusterware. Volume Groups should be attached via iSCSI and configured with SCSI-3 Persistent Reservations.
SQL Server Best Practices on AHV
These configurations should be treated as baseline for any production SQL Server on Nutanix, whether migrated or newly deployed.
Storage Layout
- Use at least four vDisks to distribute data files, log files, TempDB, and the OS independently.
- Format all data and log volumes with a 64 KB NTFS allocation unit size.
- Do not use Windows Dynamic Disks or in guest volume managers. Add vDisks directly to the VM instead.
- Keep OS, SQL binaries, user database data, logs, and TempDB on separate volumes.
Instance Level Tuning
- Instant File Initialization (IFI): Grant the SQL Server service account the “Perform Volume Maintenance Tasks” privilege to enable IFI. This eliminates zero initialization overhead during data file creation and auto growth events. IFI applies only to data files (.mdf and .ndf). Log files (.ldf) are always zero initialized regardless of this setting. Starting with SQL Server 2016, IFI can also be enabled directly from the installation wizard.
- Lock Pages in Memory (LPIM): Enable LPIM to prevent Windows from paging the SQL Server buffer pool to disk. Max Server Memory must be set correctly before enabling LPIM to avoid starving the guest OS.
- Max Server Memory: For mid to large VMs, leave 6 to 8 GB for the OS. For VMs under 32 GB of RAM, 4 GB is often sufficient. A practical formula: reserve 10% of total RAM for the OS, with a ceiling of around 8 GB unless SSIS or SSRS also run on the same instance.
- MAXDOP: Set MAXDOP to the number of logical cores within a single vNUMA node. For SQL Server 2016 and later, the updated guidance is to use either 8 or the number of cores per NUMA node, whichever is smaller.
- Cost Threshold for Parallelism (CTFP): Increase from the default of 5 to at least 50. OLTP workloads land at 50. Hybrid environments sometimes use a value in the 25 to 50 range.
- TempDB: Match the number of data files to the logical processor count when that count is 8 or fewer. Start at 8 data files when the logical processor count exceeds 8. Only increase beyond 8 (in increments of 4) if PAGELATCH_UP or PAGELATCH_SH waits confirm actual contention.
SQL Server Baseline Configuration Summary
| Setting | Recommended Baseline | Reason |
|---|---|---|
| IFI | Enabled | Eliminates zero initialization overhead for data files during creation and auto growth. |
| LPIM | Enabled | Prevents Windows from reclaiming the SQL Server buffer pool. Requires Max Server Memory to be set first. |
| Max Server Memory | Total RAM minus 4 to 8 GB (or 10% of total RAM) | Prevents SQL Server from starving the guest OS. |
| MAXDOP | 8 or cores per NUMA node, whichever is smaller | Keeps parallel query execution within a single NUMA domain. |
| CTFP | 50 (or 25 to 50 for hybrid workloads) | Prevents low cost queries from triggering parallelism on modern multi core hardware. |
| TempDB | Match logical processor count up to 8; increase by 4 only when contention is confirmed | Reduces allocation contention. All files must be equally sized with identical growth settings. |
Oracle Best Practices on AHV
Oracle on Nutanix AHV benefits from the same platform level advantages as any other workload, but the database engine has enough specific tuning requirements that it warrants its own treatment.
Memory Allocation: SGA and PGA
Reserve approximately 10 percent of the total VM memory for the guest OS and file cache. Of the remaining 90 percent, allocate 80 percent to the System Global Area (SGA) and the remaining 20 percent to the Program Global Area (PGA). Memory reservations should be set to 100% of the assigned VM memory. Memory overcommit is not recommended for Oracle workloads.
Storage Layout and Disk Groups
NDB provisions multiple vDisks spread across ASM disk groups to maximize throughput across the Distributed Storage Fabric. The two primary disk groups are DATADG for database data files and RECODG for redo logs and archive files. For Oracle RAC, a third disk group CRSDG is required for Grid Infrastructure and clusterware files.
| Disk Group | Small or Medium (500 GB and under) | Large (501 GB and above) |
|---|---|---|
| CRSDG (RAC only) | 3 vDisks | 3 vDisks |
| DATADG | 4 vDisks | 8 vDisks |
| RECODG | 2 vDisks | 4 vDisks |
ASM Configuration Options
Nutanix supports ASMFD (ASM Filter Driver), ASMLIB, and udev rules for ASM disk mappings. ASMFD is the preferred method on modern Linux distributions. All ASM disks should be placed on vDisks in an AOS storage container with inline compression enabled and deduplication disabled.
Network Design for Oracle RAC
Oracle RAC requires a public network for client connections and a private interconnect for cache fusion on separate VLANs. Mixing them on the same VLAN introduces the risk of cache fusion traffic competing with client traffic. When using NDB to provision Oracle RAC, NDB manages IP address assignment across public, private, and virtual (scan and VIP) network types.
RAC and Nutanix Volumes: Oracle RAC requires shared storage for the CRSDG disk group. On AHV, this is provided through Nutanix Volume Groups attached via iSCSI with SCSI-3 Persistent Reservations enabled. This is a prerequisite for RAC clusterware to function correctly.
Oracle Patching with NDB
NDB uses an out of place patching model for Oracle. Rather than patching a running Oracle home directly, the process involves provisioning a new database VM from an existing software profile, manually applying the patch set to that VM, and then creating a new software profile version from the patched VM. Once published, that version becomes available to all Oracle VMs managed by NDB. Patching can be performed in either a rolling or non rolling fashion for Oracle RAC environments.
Time Machine Backup and Recovery for Oracle
NDB Time Machine creates application consistent snapshots of Oracle databases along with copies of transaction log files. An SLA attached to the time machine controls snapshot frequency and retention. Point in time recovery is available as long as both a base snapshot and the covering transaction logs exist for the target timestamp. NDB restores the vDisks from the appropriate snapshot and then applies log files forward to bring the database to a consistent state.
Decommissioning Protocol
The migration is not complete when the VM powers on successfully on AHV. A structured decommissioning process ensures the legacy environment is cleaned up safely.
| Step | Action | Owner |
|---|---|---|
| 1 | Source VMs remain powered off with NIC disconnected for a 48 to 72 hour burn in period to prevent IP conflicts. | Infrastructure Team |
| 2 | Confirm with Application Owners that performance and stability on AHV is acceptable after the burn in period. | Project Lead |
| 3 | Archive a final backup of the source VM according to the organization’s retention policy before deletion. | Backup Admin |
| 4 | Remove the VM from the source cluster inventory. | Infrastructure Team |
| 5 | Update the CMDB or asset tracker to reflect the VM’s new hypervisor and decommission the legacy record. | IT Operations |
Technical Discovery Requirements
The quality of the discovery work done before migration determines how smooth everything else goes. At a minimum, the following information should be gathered before any migration plan is finalized.
General Infrastructure
- Specific vSphere version and ESXi build number in use on source hosts
- Networking configuration: LACP, Jumbo Frames (MTU 9000), or standard configuration
- IP retention requirement: retain existing IPs after migration or assign new IPs on AHV
- Guest OS list with versions and BIOS/UEFI boot mode for each VM in scope
SQL Server Environments
- SQL Server versions and editions (Standard vs. Enterprise) deployed
- Deployment type: Standalone, Failover Cluster Instance (FCI), or Always On AG
- Current vCPU to physical core allocation and whether LPIM is already configured
- vDisk layout per VM: number of disks, purpose (Data, Log, TempDB), and whether any single large data files exist that should be split
- Dependencies on MSDTC, Linked Servers, or SQL Agent Jobs that require documentation before cutover
Oracle Environments
- Oracle versions in scope and whether instances are Single Instance or RAC
- Shared storage configuration for RAC: ASM with ASMLib, ASMFD, or udev rules
- Huge Pages configuration status in the guest OS
- Existing RMAN backup workflows or Data Guard standbys that can be leveraged
- Source platform architecture: if any workloads currently run on AIX or Solaris (SPARC), be aware that Nutanix Move is strictly an x86-to-x86 tool and cannot be used for these migrations. AIX and Solaris on SPARC are Big-Endian, while Nutanix AHV runs exclusively on x86-64 (Little-Endian). Cross-endian migrations require a fully manual path using RMAN CONVERT for Oracle or an application level export and restore, and should be scoped separately from the rest of the Move migration plan.
Migration Constraints
- Maximum acceptable maintenance window for final cutover
- Average daily change rate for production databases (drives seeding bandwidth planning)
- Top 10 application functions or queries to validate Day 1 performance after migration
- Total allocated versus used storage per database environment, plus expected annual growth














