what is the difference between a sas controller and a sas raid controller?

Michael Cropper asked:

What is the difference between a sas controller and a sas raid controller? Are they the same thing, just named differently, or is the SAS Controller purely a connection point with no RAID capabilities and the SAS Raid Controller is something that can be configured (somehow?)

My answer:


A SAS HBA presents just a bunch of disks to the server independently. This is, indeed, where the acronym JBOD comes from: just a bunch of disks. If RAID is desired, the OS must provide it with software RAID.

A SAS RAID controller doesn’t present the disks independently (unless configured to do so); rather it provides hardware RAID service, and presents RAID arrays as virtual disks to the server.


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