RAID rebuilding...

in the content of Network+ and 70-290/291, what is the purpose of the parity drive in RAID 5 besides using it for rebuilding the RAID? Does it make anything faster? is data recovery impossible without the parity drive (RAID 0)? Is data recovery guaranteed to be possible with RAID 5?

I am pretty sure its not possible to recover RAID 0..but just want to see if anyone else has comments about that.

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Comments

kujayhawk93

As I understand it...

There is NO fault tolerance with RAID 0 (disk striping); if one disk fails, everything is lost

RAID 5 requires at least 3 disks, and the parity information is spread across all disks in the set; there is no dedicated parity drive. As long as only one drive fails at a time, you can recover everything, but if multiple drives fail you could be in trouble. Since RAID 5 uses striping as well, performance is enhanced.

sprkymrk

kujayhawk93 wrote:

RAID 5 requires at least 3 disks, and the parity information is spread across all disks in the set; there is no dedicated parity drive.

That's correct. For the curious, RAID 4 is like RAID 5 (striping with parity) except it DOES have a dedicated disk for parity. Don't worry about RAID 4 for the test though, it's not covered.

Danman32

RAID 5 is faster for reads if all drives are operationg, since you are reading across multiple disks. You get the same advantage as RAID 0 for reads. Writes though are slower than RAID 0, since the parity has to be calculated and written along with the data. It can be faster than no RAID at all though.

Now if a drive fails in RAID 5, even reads are slow, since the data has to be calculated through parity calculations. But unlike RAID 0, you are not dead in the water unless a second drive fails before the 1st one is restored.