Storage area networks
The grand pooh-bah of storage, the SAN is the most expensive storage option of the bunch, as well as the most complex. However, SANs provide capabilities not found in other solutions and, in the right situation, can actually end up saving a company some funds, even considering the expensive initial outlay.
SANs today come in two flavors: fibre channel, and iSCSI or IP-based SANs. Fibre channel is the most well known type of SAN, but over the last couple of years, iSCSI-based SANs have started to hit the market in a big way, mainly due to their good performance and much lower cost vs fibre channel.
SANs truly combine the best of both NAS and DAS storage. For example, with a proper implementation, you get a completely redundant storage network that is eminently expandable to hundreds of terabytes à la NAS, but you also get block-level access to the data just as you get with DAS. You also get access to data at a reasonable speed, making SANs good even for operations that require significant disk access. With a SAN, you also get centrally managed storage with the ability to provision space on-the-fly. Even better, with some implementations, you can even configure your servers with no internal storage and require that all systems boot directly from the SAN (fibre channel only).
With all of these great points, what are the downsides of a SAN? There are two major drawbacks to a SAN: cost and complexity, particularly when it comes to fibre channel implementations. A reasonable fibre channel SAN can start in the $50-60K range for just a terabyte or two of storage. On the other hand, newer SANs based on iSCSI might start in the $20-30K range, but aren't quite up to the performance levels of their fibre channel cousins. The difference in price is mostly due to iSCSI's ability to make use of off-the-shelf gigabit Ethernet hardware, whereas fibre channel requires specialised, expensive equipment.
Direct-attached Storage | Network-attached Storage
Storage-Area Networks
