Applying the SAN

By Tom Henderson, |  Storage

The software layer thus interjected into each device in the Navistor system
translates application filing-system requests into common, Esperanto-like calls to the
storage devices under the SAN OS's control. So far, Navistor has provided compatibility
with the most commonly used file systems. (See Resources, below, for Navistor's site,
which provides more details and caveats.)

SAN drives are tricky to use as boot media. This news won't break the hearts of
industry old-timers who are already suspicious of detaching all of a server's media in
favor of a SAN.

Another gotcha: No simultaneous access is allowed to the same physical data file
unless, of course, that file is read-only. (A SAN operating system won't allow you to
corrupt data through simultaneous writes, thank heaven.) And a SAN operating system
must still provide a way to find files adequately through the use of operating system
search criteria (search paths or registry entries or tree calls) or other filing-system
search methods such as Explorer.

Windows 2000 dynamic disk management won't work on a SAN -- as well it shouldn't,
since it could allow a user to dynamically repartition a shared area, to the detriment
of stability.

The app factor

During the prejudgment and appeal stages of the Napster case, a reporter on NPR's
afternoon radio show All Things Considered interviewed a fellow with an MP3
addiction. He downloads MP3 files -- more than 2,000 to date -- incessantly,
occasionally checking out the results to find "interesting music and new artists." I
think it's an obsessive-compulsive disorder, but then, many computer apps -- and
users -- suffer the same problem: Observe my 351MB personal message store ... and its

One of the best candidates for a SAN is the traditional client/server relational
database store. While there's a trend toward buying huge server memory arrays -- think
DRAM or "user memory" -- to keep relational databases in memory (as opposed to magnetic
storage), such a solution is only part of the picture.

Relational database applications require the creation of views and tables. Some
tables are dynamic and have a short life; others exist for a longer but still finite
amount of time; some live forever. An increasing reliance on the mining of data from
the data warehouse -- and on the resulting large sorts and analytical analyses -- is
driving the need for elastic storage space. The need to maintain elasticity may also
keep database views, tables, sorts, and the like, away from primary table storage and
necessitate additional space -- SAN space. Data-mining programs may build tables via
Ethernet-based queries to applications such as Oracle or SQL Server, then place those
tables elsewhere on the SAN.

The SAN-app quick list

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