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What Windows 8 Hyper-V R3 Storage Enhancements Will Mean

There are a couple of interesting storage enhancements

Last September, Microsoft released some information about what customers could expect to see in Windows 8, and at the very end of February the Windows 8 beta became available. There's been some interesting activity on the blogosphere about it (see a good blog from Jason Perlow here).

What Are the Enhancements?
There are a couple of interesting storage enhancements in Hyper-V R3, including VHDX, ODX, built-in deduplication, support for SMB 2.2 and the introduction of ReSF (Resilient File System).

VHDX: Larger Capacity VHDs
In Hyper-V R2, VHDs can be up to 2TB in size, but in Hyper-V R3 with VHDX that has increased to 64TB. While not imposing any limitations themselves, their size is limited by the native VHD capacity constraints. The expanded storage capacity nicely complements increases in CPU and memory on a per VM basis that will allow Hyper-V to host larger, higher performance applications.

ODX: Renewed Invitation to Third-Party Array Vendors
ODX is somewhat analogous to the VMware APIs for Array Integration (VAAI) concept, allowing certain tasks to be offloaded to storage array hardware to improve performance and/or lower host CPU utilization. But ODX is just an ioctl - the devil's in the details of implementation, and that falls to storage array vendors and how they implement various features. It's telling that third-party SCSI copy has been around for quite a while, but has never really caught on. Still, they are rooting for this to take off on Hyper-V because, depending on what the back-end storage implementations look like, it could be very interesting to them for two reasons.

De-duplication
Content-based deduplication is a popular topic these days, but it also has the reputation for being a resource hog. Microsoft hasn't mentioned much about any implementation details of this upcoming dedupe technology (is it file-based? Volume-based? In-line or post process? Where do the cycles come from to perform dedupe operations? etc.) but I guess that it will be an optional feature that customers can turn on or off.

NAS and Hyper-V: Yep, It's in There.
Until now, there really hasn't been a viable NAS option on Hyper-V. Windows 8 introduces support for SMB, which will allow VHDs to be hosted on shares for the first time. Windows VSS, Microsoft's snapshot API, has historically operated at the LUN level. In virtual environments, it is much more efficient to perform certain storage operations like snapshots, failover, and replication at the VHD rather than the LUN level. Doing so can save on storage capacity consumption, time, and network bandwidth. With the introduction of SMB, VSS can now operate at the share level as well. If VHDs are hosted on shares, one can potentially do snapshots, failover, and replication with increased granularity and hence, more efficiently.

Resilient File System
In ReFS, Microsoft has made reference to a new feature called "storage spaces." By letting administrators configure storage into separate virtual pools, this enhancement to the storage interface (which until Windows 8 has been through VDS) should enable larger, more scalable, and more easily managed storage configurations.

CSVs Benefit Too
Finally, Microsoft has also made some CSV enhancements. VSS backup performance for CSVs has been a challenge in the past due to the performance slowdowns often associated with re-directed I/O mode. In Windows 8, it appears they've made some modifications to how copy on write is handled during VSS operations so that updates to a snapshot during the backup process no longer force that VHD into re-directed I/O mode. These changes do not appear to apply to runtime I/O to dynamic and differencing VHDs, just VSS operations. It looks like Microsoft will also improve the scalability of backup operations by supporting concurrent backup of all VMs within a single CSV.

The bottom line here is that Windows 8 includes a lot of storage enhancements.

More Stories By Eric Burgener

Eric Burgener is vice president product management at Virsto Software. He has worked on emerging technologies for almost his entire career, with early stints at pioneering companies such as Tandem, Pyramid, Sun, Veritas, ConvergeNet, Mendocino, and Topio, among others, on fault tolerance and high availability, replication, backup, continuous data protection, and server virtualization technologies.

Over the last 25 years Eric has worked across a variety of functional areas, including sales, product management, marketing, business development, and technical support, and also spent time as an Executive in Residence with Mayfield and a storage industry analyst at Taneja Group. Before joining Virsto, he was VP of Marketing at InMage.

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