How does the Raid 5 Parity Algorithm work?

[Deezus]

Was talking with someone about computers and they made a comment about something they didn't understand. How the Algorithm in a Raid 5 parity set-up actually does it's job of restoring lost data that's... well, lost. The question goes well beyond what I know about Raid set-ups, but I can't stop thinking about it now.

I've googled it and gotten some "answers", just nothing specific enough or dumbed down enough so I can grasp how it does it.

Any help?

 

[davidlem]

Take a look here .

 

[Lazn_Work]

http://arstechnica.com/paedia/r/raid-4.html

Both RAID 3 and 5 just use an XOR. (see the next page for RAID 5, but that page doesn't explain what the XOR does edit: because it assumes you read the previous page on RAID 3 that does an excellent job of explaining XOR)

edited for the lazy:

==>Lazn

 

[Deezus]

I think that covers it.

Much appreciated.

 

[j-rock]

that page doesn't explain what the XOR does

==>Lazn

XOR is a bitwise operator. It is an exclusive or. so the bits can be 1 and 0, 0 and 1, but not 1 and 1, or 0 and 0.

example

XOR on these two bytes

11001010
00101001
--------
11100011   <--- after XOR

 

[davidlem]

Just because I love WikiPedia so much, I submit to you this.

 

[Lazn_Work]

XOR is a bitwise operator. It is an exclusive or. so the bits can be 1 and 0, 0 and 1, but not 1 and 1, or 0 and 0.

example

XOR on these two bytes

11001010
00101001
--------
11100011   <--- after XOR

Bah nevermind. If you had bothered to follow the link I provided you would see it explanes how XOR works (and a better job of it), and the reason I said anything is because the XOR explanation is on the RAID 3 page I linked to, and not the RAID 5 page (my post was not about XOR but about linking to RAID 3 and not RAID 5)

==>Lazn