Raid 5-

Hello friends,

I've always been curious to know how parity worked in a raid 5 environment. I understand that it performs striping with parity, but do all the drives in the array that are striped also hold the parity too? (seeing how there is one dedicated drive to hold all parity info and the need for at least 3 disks).

At that, what would happen if the parity drive itself failed? What's the proper protocol in dealing with that?

-Cato

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Comments

Novalith478

Parity bit - Wikipedia, the free encyclopedia

This clarified everything for me.

Krunchi

The Parity is written across all drives what you are describing is a Raid-3. Raid 5 uses a algorithm that is able to rebuild a disk if it fails that is why if you have 3 100 Gig drives the total size of the array is 200 gigs the other 100 gig is used for parity.

ptilsen

I still like to refer to this page as a great RAID reference:
Visualize Your RAID

Between that and Wikipedia, you should be all set.

No matter what drive fails, the controller or software/firmware has to initiate a rebuild once the new drive is in place. If it's done with the array still online, it will impact performance. Either way, it should take about the same amount of time regardless of which drive fails. The calculation to make the parity drive is not fundamentally different than recovering data using the parity drive.

xcato

ptilsen wrote: »

I still like to refer to this page as a great RAID reference:
....snip......

So if the parity drive was to be replaced, all the striped drives would calculate their parity info onto the newly assigned parity drive when it comes on?