ZFS question...

[Dan Nelson]

In the last episode (Apr 10), Wael Nasreddine said:
> Hello list,
> 
> I have 3 external USB hard disks hooked to my server, serving media
> files via NFS, SSHFS and samba to my local network, laptops and
> Playstation 2, the sizes of these hard disks are 160Gb, 500Gb and
> 750Gb, the 160Gb has no space left, my archive of Movies is on it, the
> 500Gb will soon run out of space it has my archive of TV series and
> anime but the 750Gb is almost empty, it has only a few Gigs for my Mp3
> collection anyway I hate to have movies/series everywhere so I thought
> of combining them into one big array... RAID0 isn't an option, RAID5
> could be but since the smallest one is 160Gb the size of the array
> will be 320Gb which is ridiculous in my case... So I thought of having
> a ZFS over the 3 drives, but I don't know what size should I expect
> and how/where can I mirror or mirroring isn't possible for me??

You don't necessarily need ZFS for this; gmirror would work just as
well.  You can split your 750GB drive into three
partitions/slices/whatevers:

160GB - mirror this with your physical 160GB disk
500GB - mirror this with your physical 500GB disk
90GB - leftover unmirrored, use at your peril

ZFS would let you take those two mirrored vdevs and stripe them into a
single pool, but then again you could use gstripe or gconcat for that. 
The main benefit to ZFS would be if you regularly crash the system;
fscking a 750gb UFS filesystem could take a while.

-- 
	Dan Nelson
	dnelson at allantgroup.com