a (hopefully) simple newbie zfs query regarding available space

[chris scott]

2009/8/9 John . <comp.john at googlemail.com>

> 2009/8/9 chris scott <kraduk at googlemail.com>:
>
> >
> > not a zfs thing is happens with all os and file systems. Basically HD
> > manufacturers quote their capacities in base 10 ie 1 TB = 1000000000
> bytes.
> > File systems are calculated in binary therefore the calculation they use
> is
> > 1024 x 1024 x 1024 = 1099511627776. Slightly more as you can see.
> >
> > Therefore 1 GB is os terms is 1073741824
> >
> > therefore hd capacity in GB is
> >
> > 1000000000000/1073741824 = 931.322575
> >
> > The extra you see is it due to HD manufactures slightly over capacity the
> > drives
> >
>
> Hi,
>
> What I meant was, I was seeing 931MB instead of 1.6TB (2x1TB disks)
> but this was because I didn't read about zfs properly (they recommend
> 3 or more disks. In the man page for zpool it says:
>
> "A  raidz group with N disks of size X with P parity disks can hold
> approximately (N-P)*X bytes
> [...]
> The recommended number is between 3 and 9"
>
> so, I'll wait till I get an array before implementing zfs. In the
> meantime, I'm using gconcat. Sorry for the noise.
>
> --
> John
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ah did you do a zpool create tank ad0
then zpool attach tank ad1 type thing?

if you did you have you have created a mirror

to fix do a zpool dettach ad1
then a zpool add ad1 to create a stripe

Having said that it not good practice to have no redundancy.

You could comprise by putting your important data on a dedicated file system
then setting copies to 2 or 3