momius - Fotolia
It will be several months before the next version of Windows Server hits enterprises, but Microsoft previewed what to expect from the new operating system, including two major storage features: Storage QoS and Storage Replica.
Storage QoS enforces bandwidth usage
Storage QoS is a brand-new storage feature that allows administrators to centrally control storage performance for Hyper-V virtual machines. If the concept of storage QoS sounds familiar, that's probably because Windows Server 2012 R2 had Quality of Service Management, a similar tool that allowed administrators to enforce minimum and maximum levels of IOPS for Hyper-V virtual machines.
Although Quality of Service management was a welcome feature for Hyper-V, it was sometimes inadequate. The feature worked at a per-host level; if multiple host servers shared a common physical storage device, then the QoS policies that had been applied would not be enforced across host server boundaries.
The new Windows Server Storage QoS feature addresses the shortcomings of the Quality of Service Management feature, specifically enforcing bandwidth usage policies across Hyper-V hosts. For storage QoS to do its job, Hyper-V VMs have to be stored on a scale-out file server cluster that must be based on Windows. Hyper-V currently can store VMs on an SMB 3.0 file share, which allows a Hyper-V cluster to store VMs on a scale-out file server cluster. The scale-out file server cluster makes the file share available via SMB 3.0.
The SMB 3.0 file share doesn't do anything on its own, other than make storage available to host servers. There are three components that make Storage QoS work. The first of these components is the Policy Manager. The Policy Manager runs on the scale-out file server cluster and is the mechanism that provides the centralized storage performance monitoring. Each server in the scale-out file server cluster also has an I/O scheduler that regulates disk I/O. Although the I/O scheduler exists at the node level within the file server cluster, the I/O scheduler's can communicate with one another.
The third component involved is the rate limiter -- a Hyper-V component; each Hyper-V server has its own rate limiter. As the name implies, the rate limiter is the mechanism that prevents Hyper-V VMs from consuming excessive bandwidth. The Policy Manager can communicate with the rate limiter to make sure that virtual machines perform according to set policies.
Storage Replica uses SMB 3.0
The second storage feature in Windows Server 2012, Storage Replica, allows block-level data replication from one Windows server to another, thereby creating two identical copies of a server. The replication process is based on SMB 3.0 and is hardware-agnostic.
Storage Replica can be used either synchronously or asynchronously. Synchronous use guarantees that the primary and the replica server are always kept perfectly in sync. Asynchronous replication has the potential for some data loss in the event that a failure occurs, but is appropriate for use in situations where the connectivity between the two servers is slow or unreliable.
Storage replication occurs at the block-level, meaning there's no concern for open or locked files. It also means that features such as file system encryption or native deduplication will not be disruptive to the replication process.
Microsoft's official guidelines for storage replication remain to be seen, but on the surface it appears it will work with virtually any new Windows server, regardless of the workload. The technology has enormous potential for improving Hyper-V. The previous version of Hyper-V includes a replication feature, but replication had to be enabled at the VM level. It simply is not practical to replicate large numbers of virtual machines using the current replication mechanism. A server level replication feature would allow the entire Hyper-V hosts to be replicated without administrators having to worry about enabling replication for individual virtual machines.