Whats the best way to calculate RAID levels?

[Tonij]

Anyone have any tips/tricks/links on the best way to get the most bang
for you buck when it comes to sizing systems that will need RAID 5?

It seems I am always taken by surprise and have a lot less space than
I think I am going to have when either getting new systems or laying
out existing ones.

I use Veritas Volume manager and some of the systems are using RAID 5
and some are using Stripe Pro...is there a reliable formula that I can
use for estimating how much "ususable" space we will have with X
amount of disks in X layout?

[UnixFan]

[email]tonij67@hotmail.com[/email] (Tonij) wrote in message news:<358db3cc.0407231334.1f4c0a8e@posting.google. com>...

> Anyone have any tips/tricks/links on the best way to get the most bang
> for you buck when it comes to sizing systems that will need RAID 5?
>
> It seems I am always taken by surprise and have a lot less space than
> I think I am going to have when either getting new systems or laying
> out existing ones.
>
> I use Veritas Volume manager and some of the systems are using RAID 5
> and some are using Stripe Pro...is there a reliable formula that I can
> use for estimating how much "ususable" space we will have with X
> amount of disks in X layout?

Roughly, from a n-column RAID 5 configuration, you could get near
(n-1)/n * 100% the total size. For a stripe-pro configuration, you
could get near 50% the size of total space.