How is the HD cache utilized in a raid-0 array?

[Nedkt]

So say I have 2 drives each with 16MB cache and I raid-0 them. Does the new "composite" drive have an equivalent of 32MB cache or 16MB? Or (as I assume) is it more complex than that?

 

[antoant]

I am not an expert in RAID but htis is how I see things. If your RAID is implemented in hardware, then the controller presents the operating system with a single drive. I don't think the OS can "see" the cache of the actual drives. Once the data reach the controller then the hardware takes over and sends the data to either of the hard disks. From there the firmware and the hardware decide how and where they are putting the data. Same thing when the OS asks for data from the HDD.

For a software implemented raid the decision on which drive the data will be stored is done by the OS and/or software. However, again the OS will send the data to the controller to be put on a certain drive. The OS does not "see" the cache or the drive directly. It is up to the controller to send the data to the drive and get the data from the drive.

 

[PCcashCow]

Software Raid can be done with one drive, and the OS does see the cache, instructions need to be sent the same of system ram. But in the simplest of terms, yes, Raid stacks improvement, and utilizes all the features for striping.