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EVA 4400 many disks in single Disk Group (RSS) with Vraid5 and "double protection". I am protected?

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Denialmix
Occasional Contributor

EVA 4400 many disks in single Disk Group (RSS) with Vraid5 and "double protection". I am protected?

As EVA 4400 works with 72 FC discs and VRAID5? Two Disks Simultaneous Failures off EVA? Thank you experts!

3 REPLIES
Johan Guldmyr
Honored Contributor
Solution

Re: EVA 4400 many disks in single Disk Group (RSS) with Vraid5 and "double protection". I

A disk group is not an RSS. A disk group may have many RSS.

 

If you create a disk group with 72 disks you'll most likely get 9 RSS with 8 disks in each (9*8 = 72).

This means your disk group can theoretically handle 9 simultaneous disk failures - one in each RSS.

 

Disk protection reserves space in the disk group ( double reserves 4 x the largest disk in the disk group ). If during reconstruction another disk fails in the same RSS the double-protection could not have helped you. However, it will make reconstruction faster because there's less amount of shuffling between disks when doing reconstruction. So indirectly it can help.

Denialmix
Occasional Contributor

Re: EVA 4400 many disks in single Disk Group (RSS) with Vraid5 and "double protection". I

Quick Response! WoW! Thank You!
Well, there is a "table" linking number of EVA disks x number disks in each RSS? It is better to divide my Disk Group?
Johan Guldmyr
Honored Contributor

Re: EVA 4400 many disks in single Disk Group (RSS) with Vraid5 and "double protection". I

There are best practices related to this. If you have an amount of disks in the disk group that is divisible by 8 that's a great start.


You should be able to find out which RSS a disk is in by looking in the output of the "controller configuration dump". It's in .xml though so it might require some digging.

 

The information was available in CV in the past but it was removed.