SAN Versus NAS: How Drive Slots Influence Performance


Storage Area Networks (SANs) offer better performance. Network Area Storage (NAS) offers a better price. What system should you choose, and what does it mean for your business?

Last time, we wrote about some of the strategy involved in choosing the optimal storage solution. Suffice it to say, purchasing both a SAN and a NAS is as much an option as buying one or the other. Now for a bit more detail on the performance side.

An NAS will have 4, 8, or 12 drive slots, depending on the unit. The smallest IBM SAN our clients use, the V3700, has 240 2 ½” slots, or 120 3 ½” slots by comparison. OK, so clearly there is a big difference between those two, but what does that mean in terms of performance?

Drives Are Like Cylinders

Nowadays, each component of a business solution is a computer, only a specialized version of one. Drives are designed for storage, but they also have Central Processing Units (CPUs) like any laptop. These work to process and send data. Each drive adds power to the overall solution and oversees processing for the data it contains.

Think of drives as cylinders in a car. Each cylinder has a certain capacity to turn fuel into power.

The IT term for horsepower is called Input/Output Operations per Second (IOPS).

More cylinders = more horsepower

More drives = more IOPS!

A SAN has a much greater power/performance potential, just from the number of drives it can handle.

Additionally, IBM SANs have enterprise-level controllers, which automatically [optimize performance based on usage – Link to Easy Tier]. This “drives” the SAN to an even higher level of sophistication and power.


We are not saying you should buy a SAN, or not buy an NAS. As we said last week, many businesses use a NAS to help them achieve a greater cost efficiency. As IT consultants, it is our job to ensure our clients find the solution/s that is/are ideally suited for their needs. We offer objective advice, based on our experience, as well as our clients’ experience. We are excited about the V3700, but our clients’ happiness always comes first.