topic VRAID Formula ? in HPE EVA Storage

VRAID Formula ?

Binh Minh — Mon, 31 Jul 2006 21:55:11 GMT

Hi every one!
I want to find the formula to calculate for my Vraid. Can you help me ?

Re: VRAID Formula ?

Uwe Zessin — Tue, 01 Aug 2006 01:14:40 GMT

You question is quite ambiguous -
what is it that you want to calculate?

- required raw space?
- number of disks from virtual disk space?
- available virtual disk space?
- ?

Re: VRAID Formula ?

raadek — Tue, 01 Aug 2006 03:05:33 GMT

I found this tool very handy with regards to Vraid usable capacity calculation:
HP StorageWorks Sizer
http://www.hp.com/go/nsssizer

After downloading & installing go to Storage Calculators in the left hand side menu.

Regards

Re: VRAID Formula ?

Binh Minh — Tue, 01 Aug 2006 03:55:33 GMT

thank !
i have 01 diskgroup with 7x146GB + 4x36GB
i want to calculate the capacity for vraid5

Re: VRAID Formula ?

Uwe Zessin — Tue, 01 Aug 2006 04:02:11 GMT

I don't have exact numbers for disk sizes handy right now, but assuming a 'protection level' of 1 and leaving about 10 raw GigaBytes free, it should be about 642 GigaBytes:

(((5*146*0.93)+(4*36*0.93))-10)/1.25

Re: VRAID Formula ?

raadek — Tue, 01 Aug 2006 04:09:17 GMT

Uwe just proved that a sheet of paper & a pencil is often better that e-tools! :)

The sizer I mentioned does not allow mixing capacities within one disk group.

Rgds

Re: VRAID Formula ?

Binh Minh — Tue, 01 Aug 2006 04:44:54 GMT

To: Uwe Zessin
why 'protection level 1' take me 2 disks ? Can you hepl me ?

Re: VRAID Formula ?

raadek — Tue, 01 Aug 2006 04:51:15 GMT

Protection level 1 means that a capacity of a single drive is reserved as a distributed hot-spare.

2nd drive is 'consumed' by Vraid5 overhead.

Rgds

Re: VRAID Formula ?

Uwe Zessin — Tue, 01 Aug 2006 04:54:37 GMT

VRAID-1 means that data is stored on two different physical disk drives. The EVA *always* binds two disk drives together as a 'pair' which it uses to store VRAID-1 data, even when you don't use any virtual disks with VRAID-1.

If one disk of such a pair fails, the EVA takes the data from the surviving disk and copies it to a new pair of disks, provided that the disk group has enough free space.

There are no dedicated spare disk drives, so the EVA needs to reserve enough space within the disk group. Setting the so-called "protection level" (which only reserves space for reconstructing redundany, but does not protect the data itself) to single (or the value 1) means the EVA will reserve space that calcultes by: 2 times the size of the largest disk in the disk group.

Re: VRAID Formula ?

Binh Minh — Tue, 01 Aug 2006 05:18:33 GMT

Thank you very much !

Re: VRAID Formula ?

Binh Minh — Tue, 01 Aug 2006 05:46:02 GMT

thank !