GG, this Fool article tends to perpetuate some misconceptions and oversimplify some concepts.
1) Compared to SAN, NAS is not quite as fast because it utilizes the office LAN (local area network) rather than a dedicated fiber network.
NTAP filers are accessed via the "the office LAN", but the data is accessed via SCSI on ealier models and via fibre channel (FC) on most current configurations. EMC systems are also accessed via "the office LAN" and the data is accessed via FC. FC is the media used by SAN as well and is what the author is calling "a dedicated fiber network". The filers' access of data does not interfere with the "office LAN" and the speed of that access is faster than an equivalently configured EMC Symmetrix. (EMC does not provide benchmark data for equivalently priced nor configured Symmetrix systems. EMC provides no benchmark data for RAID enabled systems, and all NTAP filers have RAID as an inherent part of the design. It cannot be "turned off".)
2) Also, it's [NAS] not quite as reliable, typically achieving uptime of 99.9% (which translates to 8 hours of downtime per year) or 99.99% at best (1 hour of downtime per year).
First of all, NAS is not inherently less reliable than SAN. Reliability is a function of hardware/software design, not a NAS vs SAN measure. NTAP filers in clustered configurations are achieving the 99.999% uptime, I am told. (Sorry that I can't provide a source.) Filers running in non-clustered configurations are not achieving "5 9's" but are running above 99.9%. The fact that they are not in clustered configs indicates that the user is not so sensitive to uptime and the failures are frequently attributed to power and environmental problems rather than hardware and software.
The most important point that almost all are missing is that NTAP's architectural advantage is not NAS. It is its file system called Write Anywhere File Layout (WAFL). (WAFL is patented.) Filers get their speed, reliability and simplicity of operation not from NAS, or FC or hardware but from the innovative method used to writing, reading, caching, and creating snapshots of data at a given point in time. WAFL also affords cross protocol (Windows CIFS, and UNIX NFS) security and data access. All other NAS and SAN systems (yes, ALL) use the native file systems of Windows or Unix. They are not able to overcome the complexities, inefficiencies, and incompatabilities of those two file systems. NTAP filers "look" like Windows and Unix file systems to users, hosts, and apps, but the files reside on WAFL.
Sorry for the bloat, but perhaps some of you were asleep last time I pointed these things out. They deserve reiteration if you are comparing the two companies or considering NTAP as an investment. |
