While browsing the Citrix® Support Forums last week, I came across a posting that was written by a Citrix® customer who had recently upgraded his Provisioning Services™ (PVS™) farm from version 5.6 SP1 to version 6.0 and was disappointed to find out the Read-only LUN feature in PVS had been removed.

In his posting, the individual explained that he had multiple PVS Servers in his PVS farm and wanted to enable PVS HA without having to replicate his vDisks amongst them. In other words, he did not want to create multiple LUNs (at least one per PVS Server) and then copy his vDisks between them to ensure that all his servers could access the vDisks, which is a prerequisite for PVS HA.

His argument, which is a good one, is that replicating vDisks between PVS Servers is a waste of time and disk space. After all, every time he made a change to the contents of one of his vDisks, he would have to copy the vDisk to every LUN on every other PVS Server. Not only would this be a hassle, it could also lead to inconsistent vDisk versions streamed by the PVS Servers if an updated vDisk was not copied to all the servers assigned to stream it. And why use up valuable storage space just to store copies of the same vDisks over and over again?

Rather than replicating or copying vDisks between PVS Servers every time he made any changes to them, which would introduce unnecessary data management overhead, he wanted to consolidate his vDisks onto a single volume in order to simplify image management, which has always been one of the key benefits of PVS in the first place!

Some suggestions were posed to this individual, such as using deduplication with replication or a file share to cut down on wasted storage space, but his responses to these suggestions held merit on all fronts… even with deduplication, he still wouldn’t save as much storage capacity as he would using a single LUN; and a file share has two strikes against it right out of the gate: it introduces a single point of failure, which contradicts the whole point of PVS HA, and it wouldn’t match the performance provided by his Fibre Channel storage array.

Without any other viable suggestions offered in this particular thread, the individual’s initial question, “How can we achieve PVS HA in a multi-server PVS farm without wasting time and storage?”, remained unanswered.

Thankfully, for this individual and for everyone else who has ever asked this question, there is an answer – ”Sanbolic Melio!”

Melio is distributed data management software that greatly simplifies data and storage management while enhancing application availability, scalability and performance, allowing organizations to realize the greatest return on their application, server and storage investments. Melio is Citrix-Ready™ certified for use with PVS (certification extends to XenApp™ and XenDesktop® powered by PVS), works with all industry-standard server and storage hardware as well as all SAN protocols (i.e., iSCSI, Fibre Channel, Infiniband, etc.), and runs on physical or virtual machines (hosted by XenServer™, Hyper-V™ or vSphere™).

At the core of Melio is an advanced 64-bit cluster file system called (quite appropriately) “Melio FS” that allows multiple Windows® servers to share concurrent read-and-write access to one or more common pools of (block-based) storage. The storage formatted with Melio FS can be provisioned from an external storage array on a Storage Area Network (SAN) or from local disks (DAS) installed in commodity server hardware, creating a software-based storage “appliance” that provides highly available shared storage without the upfront or ongoing costs associated with SAN storage.

Built on a symmetrical architecture, Melio FS is highly resilient (read as “no single point of failure”) with the added benefit of providing a linear improvement in performance as more servers are added to a Melio cluster. For true enterprise-class scale, this unique architecture also enables seamless infrastructure expansion, allowing more servers and storage resources to be added at any time without any disruption to user productivity.

Using Melio, all vDisks can be stored on a single volume that can be accessed by multiple PVS Servers simultaneously, enabling PVS HA for vDisk high availability and load-balancing for improved performance. The result: simplified vDisk management and maintenance, efficient use of storage resources and reduced storage cost. The best part – Melio is incredibly easy to install and use, allowing administrators to create flexible, scalable, highly available shared storage within minutes!

So for this individual and everyone else looking to enable PVS HA without the hassles and caveats associated with replication or file shares, the search is over! Sanbolic Melio is the ideal storage solution for PVS HA.

To obtain a free copy of Melio for evaluation, register at http://clients.sanbolic.com.

You can also visit our Citrix Solutions page or even better, join us this Wednesday morning, February 29th, at 11:00AM EST. / 8:00AM PST. for our latest webinar “A Unique Alternative to Replication and File Shares for Citrix PVS 6.0“. During the webinar, you’ll learn how hundreds of Citrix customers around the world are using Sanbolic Melio with PVS to achieve the greatest return on their investments in XenApp and XenDesktop. Click here to register.

Until next time,
Andy