Advantages

• Hardware RAID controllers allow the detection of defects, the detection of spare units, and the possibility of rebuilding the RAID volumnes in a transparent manner when any disk drive fails.
• The load (mainly on the system bus) is reduced, especially in configurations with many disk drives and require high data redundancy.
• The consistency checks, diagnostics and maintenance are carried out in the background by the controller without taking up precious system resources.
 

Disadvantages

• The hardware RAID controllers use their own system for managing storage units. Therefore, unlike RAID software, hard drives transferred from one system to another can not be recovered if the RAID controller does not use exactly the same firmware. It is therefore advisable to have a second card in case the first card fails.
• The cheap RAID cards are equipped with slower processors than those used in today's computers. So, their performance can actually be lower than that of RAID controllers integrated into the motherboards.
• The RAID controller is a complex hardware component and therefore may fail. Also its firmware may contain bugs, which are an additional risk of failure (a new single-point-of-failure).
• The RAID management software provided vary radically in usability and quality from one manufacturer of these RAID controllers to another. In contrast, software RAID management tools provided with an operating system are, by definition, well integrated into the operating system.
• The duration of the support for a RAID controller by its manufacturer may be shorter that that of software RAID tools provided by an operating system. Such support includes correcting bugs in the firmware, which can be critical to the reliability of the RAID arrays. This sometimes occurs when new products are introduced, making the old obsolete. The manufacturer of such RAID controllers may even fold, which is far less likely to occur to operating system companies like Microsoft.

Page

Topic

1

• Introduction
• Background

2

• RAID Types
• Software RAID
• Fake Hardware RAID

3

• Real Hardware RAID

4

• RAID Levels
• Common RAID Levels

5

• Uncommon RAID Levels

6

• Combined RAID Levels

7

• Special RAID Levels

8

• Hot Plug / Hot Swap
• Parting Words