Pros and Cons of SANs

Many people swear by SANs and would never consider using NAS; they are aware that SANs are expensive and represent cutting edge technology. They are willing to live with these downsides in order to experience the advantages they feel only SANs can offer. The following is a summary of these advantages:

SANs can serve raw devices

Neither NFS nor CIFS can serve raw devices via the network; they can only serve files. If your application requires access to a raw device, NAS is simply not an option.

SAN are more flexible
What some see as complexity, others see as flexibility. They like the features available with the filesystem or volume manager that they have purchased, and those features aren't available with NAS. While NFS and CIFS have been around for several years, the filesystem technology that the filer is using is often new, especially when compared to ufs, NTFS, or vxfs.

SANs can be faster

As discussed above, there are applications where SANs will be faster. If your application requires sustained throughput greater than what is available from the fastest filer, your only alternative si a SAN.

SAN are easier to backup
The throughput possible with a SAN makes large-scale backup and recovery much easier. In fact, large NAS environments take advantage of SAN technology in order to share a tape library and perform LAN-less backups.

SANs are also not without their foibles: The following list contains the difficulties many people have with SAN technology:

SANs are often more hype than reality
Perhaps is a few years, the vendors will have agreed upon an appropriate standard, and SAN management software will do everything it's supposed to do, with SAN equipment that's completely interoperable. I sure hope this happens

SANs are complex
The concepts of Fibre Channel, arbitrated loop, fabric login, and device virtualization aren't always esay to grasp. The concepts of NFS and CIFs seem much simpler in comparison.

SANs are expensive
Although they are getting less expensive every day, a Fibre Channel HBA still costs much more than a standard Ethernet NIC, It's simply a matter of economics of scale. More people need Ethernet than need Fibre Channel.