It is almost impossible today to separate the cost of storage along hardware and software lines. For the most part, storage products are not designed that way. They are designed to be integrated subsystems with both hardware and software elements.
You can calculate the cost per megabyte without software as the cost per megabyte of the disk drives being used. You can also do this by looking at the cost per megabyte of JBOD storage. It will be higher than bare drives but not by a huge amount.
The software is where a great deal of value and additional cost comes from in storage. It's impossible to remove software from NAS. You have to assume that you will pay something - and sometimes a great deal for the software that comprises the OS, FS and any data management functions.
There is often sophisticated connection hardware (buses, loops, etc.) that can be a major part of the cost of storage and, in these cases, the management that allows an administrator to use these features effectively is inseparable. RAID comes in many different flavors and it is software. It might be implemented in a chip but RAID is a set of algorithms. Different RAID vendors will charge different amounts for their RAID functionality. But, it is almost always tied to the hardware design and the goals of the business (HA vs. low-cost storage, etc.). Again, it is very difficult to separate the costs of software from hardware because the design encompasses both.
As the storage network industry matures and as more standards are created, this could change but don't expect it to change very quickly.
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This was first published in September 2002