Today we recorded a PRODUCT VIDEO that gives a look at the Dell EqualLogic PS5000XV. This is one of the line of SANs that EqualLogic makes, and I wanted to use my blog here to elaborate on what a SAN is, rather than turning the video into a lecture series.

So to start with, what is a SAN? SAN, in this context, stands for storage area network, which is a network dedicated to storage functions, hence the name. The EqualLogic PS series is a compact implementation of this concept. The SAN handles data at the block level, as opposed to the file level. As users, we're used to the file level. I browse to my music folder, and there are my mp3s. At the block level, you are looking at, unsurprisingly, blocks, which are collections of bytes and bits of a given length. It's a way of organizing the data at a fundamental level, and enabling more efficient data transfer. It can get a lot more technical than this, but for your sake and mine, I'm not going into it.

So that's a pretty paragraph, but what does it actually mean? It means that the SAN is a device that you attach to your network and it presents itself as storage space. Like a RAID card in a server handling its onboard drives and logical volumes, a SAN has a dedicated processor to deal with RAID volumes. The PS series can do RAID levels 10, 6, 5 and 50. There's also an accelerated RAID 6 for use with SANs containing normal hard drives and solid state drives.

Back to the network part of all this. Unlike an external hard drive that you might get from mass market retailers, you're not connecting to the SAN via USB cable. And unlike some hard drive enclosures like the Dell PowerVault MD1000 or 220s, or HP MSA20 or MSA30, you're not connecting by a SATA or SCSI cable. Instead, the SAN is connected to the network in the same way as a server or computer. It communicates through iSCSI, standing for Internet Small Computer System Interface. SCSI is a very common set of standards found in hard drives, and iSCSI simply wraps the SCSI commands inside of the Internet Protocol to allow them to be sent over a network.