PERC is an abbreviation for Poweredge Expandable RAID controller.

The PERC controllers are a range of SCSI RAID controllers sold by Dell as (64 bit) PCI cards or integrated onto the motherboards of their server systems. They are actually manufactured by other large companies (eg Adaptec, LSI etc).

The full model number looks like PERC 3/DC. This tells us four things.

  • PERC - This is a PERC controller (!)
  • 3 - This is a 3rd generation controller. Currently (early 2005), 3rd and 4th generation PERC controllers are available.
  • D - This is a dual channel controller. There are also single channel controllers, represented by "S" and quad channel controllers represented by "Q".
  • C - This is a card (ie a PCI card). Integrated controllers are represented by "I".

The controllers have a management page which can be accessed during the machine's boot process, and there is also a more advanced application, "Array Manager", which allows the controller to be configured from within Windows. Their throughput varies depending on the model of the controller, but they are certainly capable of handling RAID arrays into the terabyte range.

PERC controllers are often seen connected to internal drive cages, or to external Powervault units which can house 10 or more separate hard disks. Many newer Dell servers have on-board PERC controllers (often a PERC 4/DI). However, they sell it both "with" and "without" the controller. The hardware is always on the board, but requires a small dongle (like a daughterboard) to be plugged into a socket on the motherboard to enable the RAID option.

NB: Although PERC controllers are SCSI controllers, they, like most RAID controllers, are only designed to handle hard disks. Other SCSI devices (eg tape drives) should be connected to conventional SCSI cards, and most servers have at least one of these as well.

One day later... how on earth did Damiana get softlinked?

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