Always On

Utilized and Uninterruptible

One of the biggest advantages of storage virtualization beyond uniform management of all storage resources is the significantly better utilization of all connected storage systems and data areas. Reserve capacities that would otherwise have to be maintained on each individual storage system for spontaneous expansion of individual applications without virtualization are almost completely eliminated. Additionally, software functions such as deduplication and compression are inherited uniformly to all connected storage arrays or hard drives, thus opening up huge savings potentials.

Capacity expansion of such virtualization solutions is easily achieved by adding additional disks to existing storage systems or adding new storage systems to virtualization. Data migration, (e.g., when replacing a complete array) then takes place within the solution without interruption. The virtualization itself can also grow by adding additional nodes or appliances during operation.

Precisely Calculating the Savings Potential

If a company plans to use SAN storage virtualization, then it makes sense to compare carefully the solutions by the various vendors because the concepts are often very different, and not all of them will fit your requirements. In addition to the purchase price, license costs have a major effect. An extension or a more powerful upgrade of the solution during operation is just as much a must-have as is support for the existing storage hardware. Support for all standard drivers in your operating systems is equally important, to avoid the need to install and maintain manufacturer-specific drivers across the board.

If technologies such as VMware VVols or VAAI are already in use, the virtualization solution must of course also support these technologies. Manufacturers often indicate unrealistic savings opportunities for the use of storage virtualization, which often do not show up later on to the extent promised. Without precise data analysis in advance, reliable statements can rarely be made. Some providers perform data analysis before a purchase and even offer savings guarantees in terms of deduplication or compression, which makes it easy to compare acquisition costs and savings potential.

Five Nines for HA

HA when accessing your own data is essential for small and large companies today. Even a few hours of failure of important applications can result in considerable costs or sales losses, not to mention a data loss of even a few megabytes. These availability requirements are particularly important for a central SAN infrastructure with fibre channel and storage systems, which form the backbone of the IT infrastructure. If parts of it fails, it often affects many servers and applications, and it takes a huge amount of time and effort to bring all systems back online. The famous five nines (i.e., 99.999 percent availability) means only around five minutes downtime per year, which is equivalent to continuous availability.

But what does a highly available storage infrastructure mean and what are its criteria? The German Federal Office for Information Security (BSI) describes these criteria in the paper "M 2.354 Use of a highly available SAN solution" [1] as follows:

The term "highly available" refers here to a high level of resistance to loss events. Highly available solutions are also commonly referred to as "disaster-tolerant." In relation to the stored data of an institution, this means that a storage system is built up with the help of SAN components in such a way that

•  all data is stored at two locations,
• the SAN components of the storage solution are coupled at the two sites but are not interdependent,
• each component is configured redundantly,
• an incident at one location does not impair the functionality of the components at the second location.

On the basis of these BSI criteria, it quickly becomes clear that redundant SAN components and dual fabrics alone are not enough. The establishment of an HA storage infrastructure across two different locations is absolutely essential. Such a solution must be well planned and well thought out to implement all of the company's requirements. The most effective way to implement such concepts is with a SAN virtualization solution.

Especially when it comes to HA, such solutions achieve high scores compared with conventional storage systems. When implementing such a project, all existing storage systems can continue to be used. Virtualization slots in between the existing storage infrastructure and the servers. All leading memory manufacturers have products in their portfolios that use similar technical approaches. The requirements for such an HA solution are high and correspondingly complex to implement and operate.