Re: Making a RAID array
- From: james.dore@xxxxxxxxxxxx (James Dore)
- Date: Thu, 14 Sep 2006 14:58:14 +0100
macfizz@xxxxxxxxx <macfizz@xxxxxxxxx> wrote:
Sadly, I can't afford an XServe RAID. I've been wondering about how
hard it might be to set up my own RAID array. I could do it with a set
of Firewire or USB2 enclosures (I have a four-way USB2 card in another
PowerMac that I could use). But I'd like to do it all in one box. So my
idea was to get an old Gigabit PowerMac and fit it with 4 or more
internal disks, and then set it up to do RAID.
Has anyone done anything similar? I'm guessing I'd have to get a IDE
card to provide me with two additional channels, unless I dispense with
the CD. But I don't know how I would then physically fit in the extra
two drives.
I know I could get one of these Linux-based NAS boxes and add some big
disks to that, but I'd like to see how easy it is to do it in the Mac
world.
Any pointers much appreciated.
I'm attempting something similar, only I bought a SCSI card and an
external disk box from eBay.
I've been doing some experimenting with the software raid provided by
Mac OS X and found the following.
- I can combine any number of disks into a RAID 0 (striped) disk. This
is fine for making a big drive but is useless for redundancy, in that if
one of the disks fails, I lose data on that disk., eg I can make two
arrays of six disks each of equal size, or one array of twelve disks, or
an array of four with eight separate disks...
- I can combine two disks to make a mirrored pair. This gives
redundancy, but only for one disk. If I add disks to the mirror set, I
have an array of (say) 9Gb with two 9Gb disks as mirrors.
Things I can't do:
Mirror one raid 0 array to another - eg make two arrays of six disks,
and make array B a mirror of A - this is my desired scenario, since I
get one big drive that has redundancy. (So-called RAID 10)
- at least I /think/ I can't do it. If anyone knows better, lemme know!
There is some software around that does this, SoftRaid 3 looks promising
- http://www.softraid.com/vsapple.html - and there are other items
mentioned in VersionTracker, but they don't get promising reviews.
This may all be moot, if Apple pull their finger out and we get the ZFS
filing system, which is much more like I'm used to with netware. You
don't have one-filesystem-per-disk and RAID them, you have one or more
Pools, and actual disk units are just free space to be added to a Pool.
You can mirror pools for redundancy.
Useful links:
RAID info: http://www.acnc.com/04_00.html
zfs: http://en.wikipedia.org/wiki/Zfs
NSS, zfs' ideological parent,
http://en.wikipedia.org/wiki/Novell_Storage_Services
Cheers,
--
james dore
TR7 v8 for sale: http://www.new.ox.ac.uk/~james/triumph
.
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- Making a RAID array
- From: macfizz@xxxxxxxxx
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