Why is Hardware RAID So Expensive?

[Slaimus]

Why do hardware RAID controllers need to have its own processor just to do XOR operations? Isn't XOR one of the simplest gates to build? I am sure modern IDE controllers can spare a few transisters.

What is the reason that these RAID controllers need a whole general purpose CPU for XOR?

 

[Slaimus]

bump

 

[Fullmetal Chocobo]

That is the whole reason that they are fast. They have the processor to perform the RAID calculations quickly. It makes perfect sense to me. If you cringe when someone talks about software RAID through windows, you know what I mean.

 

[Cerb]

They are small computers on cards.
CPU? Check.
RAM? Check (often expandable).
OS? Check (firmware).
Peripheral communications capabilities? Check (drive controllers, talking to the PC via PCI, PCI-X, PCI-E).

Why do they need all of this? Speed and flexibility. What happens if you stick it in a chip, and you run into a compatibility problem? Or what if you have some fancy admin app you want to use? You're screwed. Using a moderately generic CPU and very light OS helps deal with that. RAM as cache allows speed boosts without sacrificing data integrity.

The CPUs on the cards are very powerful for what they do. It's mostly simple integer work, memory management, and routing, as far as the work load goes. Processors with tons of capability at these things can be made fairly cheap, not making it worthwhile to build your own hardware for it.