vraid and raid

[worldchamp]

HI Guru
I am new in Storage era.
can anyone know abut difrnce betn vraid and raid. and how it works

Thnx in advance

[Torsten.]

"vraid" is usually used related to EVAs - virtual raids inside a virtual array.


Short: a "classic" raid resides on a fixed set of disks (e.g. a RAID 1 on a pair of disks), the vraid is placed on many physical disks (let's say all in a diskgroup), so a vRAID1 is probably using the same number of physical disks (and even the same disks) as a vraid5 or vraid6 does.



from manual:

Virtualization technologyâ Vraid, enables data to be distributed from 8 to 240 disks to increase
disk spindle count far beyond traditional RAID sets. This virtualization method also optimizes
storage for the best performance of a speciï¬ cconï¬ guration and application. Enterprise Virtual
Array eliminates tedious management functions to provide the best performance possible

[krusty]

I heard another term the other day that might apply - "Wide striping". Not the discrete amount of disks for data and parity, but more of a "float"

Curt

[Johan Guldmyr]

Hey, it's a little different between the levels of vraid.

On the EVA a vraid1 gives exactly half of the disks for usable capacity - if there is an even amount of disks in the EVA.
Each physical disk is mirrored to another physical disk in a disk group/vraid1. A mirrored pair.

A vraid5 uses 1/8 of the disks for parity - if the amount of disks in each RSS are dividible by 8. There are other threads in this forum about RSS, is worth checking out and quite central to understanding vraid.

So for vraid5 - let's say you have 40 physical disks in a disk group. On the disk group you create a vdisk. This vdisk will have data stored on all the physical disks. Optimally you will in this case have 5 underlying raid5s (RSS - redundant storage set) in the disk group. If you have maximum luck/unluck in _each_ underlying raid5 you will be able to lose one disk.