Building your own RAID.

There are a few other categories to consider when it comes to RAID.

Software RAID
Software RAID is an umbrella term meaning the CPU takes the load for the calculations, often at the behest of the OS.

Some low end cards and motherboard controllers, while supporting RAID 0, 1, 0+1 and 1+0 fine, also claim support for RAID 5. Since they don’t have dedicated hardware units to calculate parity (a good indication is a lack of RAM, and no mentioning of a XOR engine or processor), and as such simply exist as port extenders. They still provide the functions of faking out the operating system that a single disk exists rather than multiple – but all the work is done by the CPU.

Hardware RAID
Big bastard cards starting at a grand, and the ones we have featured here. These suckers have dedicated units to processing parity, offloading the duty from the CPU. This helps to improve speeds all around.

Clever cards actually write RAID data to the drives, so in the event of controller failure the array can be successfully recovered by another controller with little issue. Of course, whether it can be recovered by a different brand of controller is something different altogether.

Capacity expansion
Adding extra drives to an already existing array is purely dependent on the hardware or the software you are using, and whether a valid ‘grow’ can be performed conceptually within the RAID level. Usually needs to be supported by the controller.

Global hot spares
A global hot spare is a hard drive that is not part of any RAID set, but should a hard drive fail in an array, it is commissioned into active duty within that set. Basically, it means you don’t have to suffer degraded operation as the replacement hard drive is already there. Your controller will have to support this to automate the process, otherwise you’ll be rebuilding the array manually.

Battery backup
Fancy controllers have battery backup. During power failure, data that was mid-transfer through the controller’s cache can be dumped to another storage area once power resumes.

Sequential Read Speeds

Sequential Write Speeds