The digital age has created a world where data continues to grow in staggering numbers. This means that businesses need increasingly new storage infrastructure to ensure seamless resource management. Storage vMotion is a powerful technology which we will dive into in this blog, including what it is, how it works, real-world use-cases, and how it relates to ‘normal’ vMotion.
First, let’s start with the official explanation from VMware of what Storage vMotion is:
“With Storage vMotion, you can migrate a virtual machine and its disk files from one datastore to another while the virtual machine is running. With Storage vMotion, you can move virtual machines off of arrays for maintenance purposes or to perform an upgrade. You also have the flexibility to optimize disks for performance, or to transform disk types, which you can use as a technique to reclaim space.”
What is the difference between vMotion and Storage vMotion?
VMware vMotion and Storage vMotion are both features provided by VMware for their virtualization platform vSphere, but they serve different purposes:
vMotion
vMotion is a (licensed) feature that enables the live migration of a running virtual machine (VM) from one physical host to another within the same VMware vSphere cluster. The migration of the VM (including its memory, CPU, and network state) is done without any disruption to the VM, ensuring continuous availability of the applications and services running on it.
The primary benefits of vMotion include balancing the load over the underlying hardware platform resources and providing the ability to perform hardware maintenance without any impact.
Storage vMotion
Storage vMotion (or SvMotion) is a (licensed) feature that allows the live migration of a running VM’s virtual disk files from one datastore to another within the same VMware vSphere cluster. The VM’s compute resources remain on the same host, but its storage is moved to a different storage device without any downtime.
Storage vMotion allows IT administrators to move VMs between datastores to optimize storage usage, improve performance by placing VMs on faster storage, and perform storage maintenance or upgrades without disrupting the VMs.
In summary, vMotion is used for live migrations of VMs between physical hosts, while Storage vMotion is used for live migrations of VM storage between datastores. Both features are essential for managing a VMware vSphere environment efficiently and ensuring high availability of virtualized workloads.
How Storage vMotion works
Without going into the technical details, which you can find on the VMware website, the main take-away is that it copies the content of the virtual disk from the source datastore to the destination datastore. During this copy action, it keeps track of the changes (CBT or change block tracking) to ensure data integrity and that the source and destination datastores are in sync.
Once the copy has completed, the VM continues its operation on the destination datastore and the original virtual disk files are deleted.
A pre-requisite for the Storage vMotion to succeed is a stable environment, which includes a stable (and fast) network between hypervisors and storage.
What is Storage vMotion used for?
There are several use-cases in which vMotion and SvMotion can benefit organizations and IT administrators.
Performance Optimization
Nowadays, with the rise of superfast NVMe SSD powered storage arrays, organizations want to be able to take full advantage of that storage performance for VM’s and applications that require it. SvMotion gives them the possibility to move the high demanding workload to that faster storage array when needed without any downtime involved.
Planned Maintenance on Storage Systems
Maintenance on the core infrastructure of your platform, especially if it involves downtime, is always difficult to schedule. With SvMotion maintenance can be done on the storage systems without any impact on the running VM’s. The Virtual Machines are relocated to a different storage system which makes it possible to do maintenance on the primary storage.
Optimizing Storage Costs
Using SvMotion means you can balance and optimize workload and costs to run the VM where it is the most effective, both in terms of performance and cost-wise.
There is no ‘one-size-fits-all’ when it comes to storage. Different applications have different storage requirements. A high demanding database server virtual machine will have different requirements on the storage performance than a webserver that is only used for testing. Running both VM’s on the same storage means the webserver VM will be using unnecessary high performing storage (and the costs that come with it) or the database server VM will be underpowered because the storage is not designed for these kinds of workloads.
Another benefit is the possibility to change the virtual disk type from thick to thin provisioned. It will reduce the footprint of VM on the storage, only the actual used blocks are allocated on the storage, reclaiming unused diskspace and thus costs.
Does Storage vMotion need downtime?
No, downtime is not required. A big advantage of SvMotion is that it allows for uninterrupted relocation of a VM’s virtual disks. However, be aware that it does require substantial network resources, and this may impact the performance of other VM’s.
Does vMotion require shared storage?
No, shared storage is not required. Although in most cases SvMotion is used to relocate virtual disks between different storage systems, it can also be used to move a VM from a local datastore on one hypervisor to a local datastore on another hypervisor, this in combination with ‘normal’ vMotion. vMotion can also be used to migrate virtual machines across vCenter Server instances.
Can I automate Storage vMotion?
The API of VMware vCenter makes it possible to write automation for SvMotion if you want to be in full control when a VM’s virtual disk is relocated.
Another possibility is to let VMware handle this. One of the cool things VMware provides is Storage DRS. Storage DRS is an intelligent vCenter Server feature for efficiently managing (VMFS and NFS) storage, similar to DRS which optimizes the performance and resources of your vSphere cluster.
Storage DRS uses 2 key metrics (space and IO) to find the best datastore to place the VM virtual disks in and will seamlessly migrate the virtual disks if needed.
Leaseweb Storage vMotion
Leaseweb uses vMotion and Storage vMotion in the Leaseweb Cloud products (VMware vCloud, VMware HCI and VMware vSphere). It provides Leaseweb customers with the necessary peace of mind when it comes to running their workload environment in a Leaseweb managed VMware Cloud. Feel free to contact us if you have any questions or concerns.