[OpenIndiana-discuss] Formula raidz storage space caclulation

[Randy S]

Thanks!
Couldn't have been explained any clearer.


> Date: Tue, 8 Apr 2014 18:03:37 +0200
> From: jimklimov at cos.ru
> To: openindiana-discuss at openindiana.org
> Subject: Re: [OpenIndiana-discuss] Formula raidz storage space caclulation
> 
> On 2014-04-08 17:05, Randy S wrote:
> > Hi,
> >
> > yes even if you incorporate the kilo=1024
> > example:
> > I filled in the example below on the site:
> > RAID Mode: z1
> > Disk Size: 3 tb
> > Quantity of Disks: 10
> >
> > RAID-Z
> > *Raw Storage: 30.0 TB / 30000.0 GB
> > *Usable Storage: 24.6 TB / 25145.7 GB
> > RAID-Z uses one disk for Parity much like RAID5 and requires at least three drives to be used.
> > *Usable storage is the actual post-format amount where kilo = 1024, not 1000
> >
> > If I use the (n-1)formula this would amount to:
> > (10-1) * 3 TB = 27 TB (27000 GB)
> > even if you use 1 TB=1024 GB:
> > (10-1) * 3072 GB = 27.648 GB
> >
> > Somewhere theres about 2.5 TB being used for something in their calculations.
> > Maybe someone can explain or show me where my calculation is going wrong?
> 
> 1024 vs 1000 is another way around: a 3TB disk is
> 3000000000000 / 1024 / 1024 / 1024 / 1024 = 2.72Tb  or
> 3000000000000 / 1024 / 1024 / 1024 = 2793.97Gb
> 
> Times 9, and that amounts to 24.55Tb or 25145.7Gb
> 
> (I am sometimes confused by "b" vs. "B" in such decimal vs. binary
> notations, so maybe that should have been written another way around)
> 
> HTH,
> //Jim
> 
> 
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