RAID arrays offer a whole host of features, and we would like to touch on two of these before getting to the nitty-gritty of the controllers themselves. Setting up your RAID array is not the only matter you need to be concerned about.
Online Capacity Expansion
Online capacity expansion is recommended for forward-thinking users. When this feature is supported, you will be able to change the size of your array on the fly. This is a real boon if you intend to enlarge your array. For example: you want to replace four 160 GB hard disks with four 250 GB drives to increase your overall storage capacity. You simply swap one drive at a time for a larger one and then use the rebuild option. Once you have replaced all four drives, you can increase your total capacity on the fly.
RAID Level Migration
When we talk about RAID level migration, we mean changing from one RAID level to another. If you wish to migrate from RAID 5 to a faster RAID 0 setup to improve performance, this is perfectly possible - as long as migration is supported by the RAID controller and its software.
SATA-RAID: Should It Be Plain Old Vanilla Or Bells And Whistles?
Right at the outset of our tests, it was clear that SATA controllers can be divided into two, distinct categories. First there are the low-cost types, marketed as entry-level cards for the server market. Then there are those from the large controller specialists, who have incorporated the sum total of their available know-how into a premium product at a premium price.
Deciding whether to invest in an expensive solution, or whether a simpler model will suffice, is by no means easy. We would advise you to look closely at what you will be using the controller for. A versatile, expensive controller very rarely makes sense for the average Web server, since RAID 1 offers the same performance in many cases. High storage capacity is seldom needed for such an application.
File and workgroup servers are a different matter. The "core" of every small company should be available 24 hours a day, seven days a week and 365 days a year. As lack of space can quickly become an issue here, consider the points we have already mentioned in case of doubt.