Shared storage was once a simple animal. The abstraction between servers and storage made it possible for the server to use storage without any direct knowledge of exactly what it was or how it was configured. This was a great thing for the industry because it allowed storage interconnect standards such as Fibre Channel and iSCSI to allow interoperability between just about any compliant server operating system and storage array.
All that is starting to change. Over time, storage vendors have come out with proprietary, server-based software to allow servers to work more intelligently with storage. At first, it was common to see multipath IO DSMs (device-specific modules) such as EMC's PowerPath. These packages allowed the server to intelligently balance the flow of data over multiple physical paths to the storage device, direct traffic to the most advantageous storage controller port, and transparently work around fabric failures.
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Today, these software offerings have become much deeper and more feature-rich. Most of the major storage vendors now supply software that makes it possible to take application-aware SAN snapshots. These packages allow the application -- usually database platforms such as Oracle or Microsoft SQL -- to make sure their data is in a consistent state before the SAN creates its snapshot. In many cases, these snapshots can be simultaneously leveraged by backup software to make application-consistent direct from SAN backups.
That's by no means the end of the story. For example, a few weeks ago Dell announced the availability of an early production release of the new 5.0.0 firmware for its EqualLogic PeerStorage array family. Among the many improvements in array and management interface functionality, this release introduces support for VMware's vStorage APIs for Array Integration (dubbed VAAI).