Raid? A little fuzzy on it.

Well, the topic is qiute large so instead of writing it all here I'll give you two links with short overviews of RAID:
http://www.amsstorage.com/html/raid_overview.html
http://www.storage.ibm.com/hardsoft/diskdrls/ramref/ramref5.htm

They'll give you the picture needed. If you'll have more questions - mail me.

Good luck,
Ivan

RAID stands for Redundant Array of Inexpensive Disks. In other words, a set of disks (an array, at least 2 disks) that are presented to your OS as one , and that have some level of fault tolerance built in (redundant).
What kind of fault tolerancedepends on the "RAID level" you chose. RAID 1 is for example the same as "Mirroring". Except that not your OS, but your hardware, the RAID controller, takes care of the mirroring. Your OS just sees a virtual disk.
What's the purpose of a RAID? Mostly two things: speed and fault tolerance. Speed you get because your controller is capable of reading/writing to all the disks of your RAID at the same time. Very simply put: if a disk can read 1 bit per second, and you have a set of 6 disks inyour RAID, you read 6 bits per second. Even if you take the time needed to split up the data for your disks, you still gain a lot of speed.
And fault tolerance you get because in most cases you'll use some kind of RAID "level" that will allow you to loose a disk, and still keep your data. And when the faulty disk is replaced, the controller can rebuild the data based on what the other disks have. This is done by simply copying from another disk, if mirroring is chosen, but there are more soficticated methods, that put some kind of a checksum on one or more disks, and the combination of the data that is on all disks and that checksum enables your controller to rebuild the replaced disk. On line.

Jim

Check out www.webopedia.com. Do a search for RAID or any other key word for a good explination of it, plus some helpful links.

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