Simplify Array Migrations and Storage Upgrades
VMware vSphere® Storage vMotion® enables live migration of virtual machine disk files within and across storage arrays without service disruptions. Non-disruptive virtual machine disk file migration to different classes of storage enables cost-effective management of virtual machine disks as part of a tiered storage strategy.
- Perform zero-downtime storage migrations with complete transaction integrity.
- Migrate the disk files of virtual machines running any supported operating system on any supported server hardware.
- Perform live migration of virtual machine disk files across any Fibre Channel, iSCSI, FCoE and NFS storage system supported by VMware vSphere.
Dynamically Optimize Storage I/O Performance
vMotion optimizes storage I/O performance by non-disruptively moving disk files to alternative LUNs that are better architected to deliver the required performance. Cut costs by eliminating over-allocation of storage resources in order to deal with I/O bottlenecks.
- Manage storage performance issues without scheduled downtime.
- Proactively deal with storage bottlenecks before they become major issues.
- Benefit from the core technology behind VMware vSphere® Storage DRS™ for automating storage performance management.
Manage Storage Capacity More Efficiently
Reclaim unused or “stranded” storage capacity and allocate to other virtual machines. Storage vMotion enables efficient storage utilization to avoid performance problems by non-disruptively moving virtual machines to larger capacity storage LUNs as virtual machine disk files approach their total available LUN size limits. Unused storage capacity can be reclaimed.
- Move virtual machine disk files between different classes of storage as project needs change.
- Migrate virtual machines with highest performance needs to newly acquired storage.
- Shift lower priority machines to slower or older arrays, freeing high-performance storage for more important workloads.
Mirror Mode vs. Change Block Tracking
Prior to vSphere 5.0, Storage vMotion used a mechanism called Change Block Tracking (CBT). This method used iterative copy passes to first copy all blocks in a VMDK to the destination datastore, then used the changed block tracking map to copy blocks that were modified on the source during the previous copy pass to the destination.
For vSphere 5.0 and later, Storage vMotion uses a new method called Mirror Mode. At the high level, Mirror Mode uses a one-pass data copy from source to destination datastore, with changed blocks on the source datastore mirrored to the destination. Storage vMotion uses the VMkernel Datamover to perform that data transfer between source and destination datastores, while the Mirror Driver manages how virtual machine writes are applied during the copy.
Serial vs. Parallel Disk Copies
In vSphere 5.1 and later, you can perform up to four parallel disk copies per Storage vMotion operation. In previous versions, vSphere serially copied disks belonging to a virtual machine. For example, if a request to copy six disks in a single Storage vMotion operation is received, the first four copies are initiated simultaneously. Then, as soon as one of the first four finishes, the next disk copy is started.
Moving disks between different datastores in a single Storage vMotion operation should speed the process significantly. You are allowed eight concurrent Storage vMotion operations, which doesn’t directly relate to the parallel disk copy change. For example, even if only one Storage vMotion operation is issued (leaving room for another seven operations on the target datastores), that single operation might be to move multiple disks related to a virtual machine.