Enterprises turning to Virtual Desktop Infrastructure (VDI) to centralise the desktop environment at the datacentre level have a nasty surprise in store: instead of decreasing IT and management costs, VDI can cost up to 20 per cent more to administer than traditional desktop architectures.
Consider this simple metaphor. In a VDI infrastructure the host server is your primary CPU/memory and your storage is your hard disk. In this context, it is easy to see how centralised storage becomes a critical (and with traditional enterprise storage, expensive) component in getting VDI to work properly.
The storage or hard disk on a PC has traditionally been treated as a commodity component, with the price per terabyte (TB) on a PC falling rapidly over the years. This is not true for centralised storage, however, where the price per TB on a SAN or a NAS is still very high.
The second difference is functionality. Centralised storage has different use and load patterns from a standalone PC. Disk I/O is not an issue for the PC because it is optimised for a single-user environment.
In a VDI environment, the increased volume of users results in a huge amount of random read-and-write access. This puts strain on the system and most of the storage design requirements will break if the peak and median I/O throughputs are not given due consideration.
The final difference is reliability – a key requirement when designing central storage for VDI. Ultimately, storage systems need to interface with hardware with physical moving parts that tend to break down over time. Any storage system assembled to support VDI should have an architecture that takes into account the fact that hardware will fail.
Enterprises are also finding VDI environments do not live up to their cost-saving promise. This is because leading storage vendors are still selling costly proprietary systems that lock customers into closed architectures. Vendors charge premium prices for the industry standard hardware they supply by locking in customers with their proprietary on-disk formats and file systems. But change is on the way, in my opinion.
Open storage promises to end vendor lock-in, return control to the channel and end users, while reduce the incredibly high cost of enterprise-class storage. And you can still earn good margins.
In much the same way that Linux and Intel commoditised the server market, open source-based storage software that runs on industry-standard hardware can slash IT spend without any compromise in performance. Such storage software can be based on the ZFS file system, meaning no special hardware is required.
ZFS uses its end-to-end check-sums to detect and correct silent data corruption. If a disk returns bad data transiently, ZFS will detect it and retry the read.
If the disk is part of a mirror or RAID-Z group, ZFS will detect and correct the error: it will use the check-sum to determine which copy is correct, provide good data to the application, and repair the damaged copy. There is no need to modify applications. The process is automatic and works with cheaper disks.
Hybrid storage infrastructure can manage data placement transparently, holding copies of frequently-used data in fast SSDs while storing less frequently accessed data in slower, cheaper mechanical disks. The application data set can be completely isolated from slower mechanical disk drives, promising improved performance and RoI. This helps address the I/O issues of VDI.
A VDI environment is often required to provide groups of users with the same type of profiled desktops. But open source-based storage software exists that can replicate virtual disks quickly without consuming disk space. Deploying hundreds of desktops can be achieved in minutes or a few hours rather than a couple of days or weeks. In my view, this is an opportunity for the channel – particularly because this feature cannot be matched by traditional storage vendors.
This can help VDI environments live up to the promise of lower costs and fewer headaches, in my opinion.
Evan Powell is chief executive officer of Nexenta
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