On Wed, Jun 24, 2009 at 10:45 AM, David Lum <[email protected]> wrote: > Does matching HDD spindle speed matter when you are RAID-ing arrays?
Define "matter". :) You won't loose data. The RAID controller has no way of knowing how fast the spindle is spinning. It sends a request to the drive and it waits for the request to complete. There is going to be a timeout value but it has nothing to do with how fast the drives are; it's an absolute timer (e.g., "if no response within 10 seconds, fail the drive"). It's not even a case of "the whole array will only go as fast as your slowest drive". It's not like there's a set of gears inside the RAID controller connected to the spindles. :) If a request hits a slower drive, the controller will have to wait for the slower drive. How often that will happen depends on array configuration and the I/O load from the host. A RAID controller is just a specialized microprocessor, a SCSI controller (or SATA or whatever), a host interface (PCI, PCIe, etc.), some firmware, and maybe some RAM for caching. The firmware includes the software the microprocessor executes to the RAID work. Think of it like an OS, but rather than being general-purpose like Windows, it just does RAID. Better controllers have dedicated hardware for the RAID operations, but still have firmware to supervise the thing. The microprocessor talks to the SCSI controller to talk to each drive, and talks to the host interface to talk to the device driver on the OS. Conceptually, it's doing the same thing "software RAID" does; it's just on dedicated hardware so it's independent of the host computer, and thus speed and reliability are independent as well. -- Ben ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
