12 different harddrives in a "raid" array?

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My friend mentioned some software he heard of that lets you put several
different harddrives into a raid-like array. He mentioned using a bunch of
old HD's like a 40gig a 120gig a 300gig.. using an old computer..

I've got a ton of old hd's around.. they'd probably add up to over a
terabyte.. Any suggestions on how I could (cheaply) create some kind of raid
array? I'm thinking using an old computer.. add an extra s-ata controller, a
bunch more ports etc.. expand the ide so it can handle more then 4 (how do i
do this?) Some kind of software (linux based?) that mimics raid?

etc etc... any thoughts/suggestions welcomed

Re: 12 different harddrives in a "raid" array?

news.astraweb.com wrote:
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What you describe would be a JBOD (just big old disk) controller -- it
combines the capacity of whatever happens to be attached to it into what
looks like a single disk. Very problematic -- any single drive failing will
pretty much wipe out the whole virtual disk. Imagine a single disk where a
large contiguous bunch of blocks has gone bad at the same time. I've never
seen any controllers that will take twelve old-style drives either. The
ribbon connectors are just not conducive to that sort of thing.

John McGaw
[Knoxville, TN, USA]

Re: 12 different harddrives in a "raid" array?

John McGaw wrote:
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Yep it's a very bad idea all right...

for the price of all the controllers one would need...

a new , large HD could be purchased

Re: 12 different harddrives in a "raid" array?

philo wrote:
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The rational way IMHO would be either one big new disk (good) or two big
new disks in a mirrored setup (better). If one shops well 1.5tB drives are
almost reasonably priced and almost every MB seems to have support for
mirrored pairs.

John McGaw
[Knoxville, TN, USA]

Re: 12 different harddrives in a "raid" array?

On Tue, 04 Aug 2009 09:12:52 -0400, John McGaw

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I wouldn't say almost every MB, with OEM systems being the
most popular and Intel being the most popular chipset there
are a lot of boards out there, probably the majority with
the non-"R" Intel southbridges having no form of RAID
support (even level 1 mirroring).

Re: 12 different harddrives in a "raid" array?

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Given that you want to run this on an old computer don't start with
RAID. Take a look at NAS systems. Some include their own RAID-like
methods of managing disks and at least one is free.


Re: 12 different harddrives in a "raid" array?

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Other posters have already given you some good advice: a RAID 0
array will be the simplest way of doing things but reliability
would be a serious issue, especially since we are dealing with
older drives from the outset.

To preserve the reliability (or indeed enhance it) you need a more
sophisticated arrangement but the differing sized hard drives are
working against you.  The only way I can think of doing it would
be a two-level RAID arrangment.  To avoid wasting large amounts
of disk space I would be thinking in terms of RAID 50 or 55.  To
do this in hardware you would probably be looking at at least a
mid-range SAS controller but the cost for one of those is broadly
comparable to a reasonable gaming machine: that is not remotely
viable from an economic perspective so you are looking at software

In terms of physically connecting everything to you machine I would
go for simplicity and make everything SATA.  Convert your IDE drives
to SATA with adapters and connect them all up via multiplexors.
These are likely to add up and themselves may be enough to make it
a complete non-starter.

Next you need to figure out how to slice up your disks: for you
smaller drives the entire drive could be only one slice but the
larger ones may have two or more slices on them.  Within each
first-level RAID 5 array the slices need to be the same size
(although they can differ between arrays) and to preserve redundancy
no more than one slice in the same array should reside on the same
physical disk.

The next layer is combining those arrays in turn into a single
array.  If you can manage a reasonable number of identically sized
arrays then there is nothing to stop you RAID 5-ing those as well.
If not you are looking at RAID 0 and relying on the intrinsic
reliability of the individual arrays.

Performance is not likely to be exceptional but it should not be
truly sluggish either provided there is enough free CPU to accomodate
two layers of software RAID.  Given the price of a couple of TB
hard drives I doubt it would be economically viable but it is
certianly possible.

Andrew Smallshaw

Re: 12 different harddrives in a "raid" array?

On Sun, 2 Aug 2009 17:07:00 -0400, "news.astraweb.com"

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It's not worthwhile.  If you insist on doing it then most of
the rest of what I've written will be a waste of your time
and so you should stop reading now.

First, the old computer PSU is probably not viable for long
term use due to age.  Second it is unlikely to be able to
support so many hard drives due to a limited 12V rail
current even if the drives were on a rather expensive
controller with staggered spinup... unless the computer
isn't really very old and was overbuilt when new so you have
quite a bit of excess PSU capacity remaining.

How big is this old computer?  Many full towers can't fit 12
hard drives, particularly the older ATX generations couldn't
even if all the top 5.25" bays were filled.

The age of some of the drives is bound to make them a
liability.  Normally someone makes a redundant array to
overcome failures but in this case with so many old drives
and an old PSU and system, odds start increasing that you
could end up having a 2nd failure before you resolve the
first one.

If you were only wanting to run as many drives as the
motherboard controller or a single raid card supports, the
newer drives I mean, it might seem viable in some instances.
In the described situation it would be making an
unnecessarily complex and potentially failure prone setup
without much good reason.

A 1TB HDD can now be had for about $75 (in the US), if 1TB
of data is worth storing then surely it is worth at least
the cost of a couple 1TB HDDs mirrored into a RAID1 using an
inexpensive (~$20) software raid controller if the intended
motherboard doesn't have integral RAID support.

The problem with software that mimics raid is you must have
that software running and configured to do so.  What if the
OS installation or software crashes?  What if you need the
data back online soon?  What if the system has a hardware
failure and you need to pull the drives and connect in
another system?  What if you have to run drive diagnostics
which don't realize there is an OS based soft-raid?

I haven't even mentioned the added level of noise from so
many hard drives, possibly some of them old enough to use
ball bearings in the motor which could be quite loud by now,
and the increase on the power bill and need for increased
chassis cooling and ultimately, a hotter running room or
higher air conditioning costs.

If you really want to build a very elaborate 12 drive
fileserver, then I recommend starting out with 12 new modern
hard drives, new PSU, new motherboard, proper hardware raid
card(s), etc... going all the way to build something worth
the time and headaches if something goes wrong, something
you can hope will last (besides periodic HDD rotations to
preceed as many failures as possible) 10 years or more.

This is a more reasonable goal than some might think, today
we have relatively low power CPUs more than adequate,
gigabytes of memory for less than $30, PCIe for ample
bandwidth and new enough tech that it won't be replaced with
something substantially more fit for the purpose any year
soon, unless yesteryear PCs with PCI slots that have to
share 133MB/s with all drives, all other PCI devices... and
that's if you have a good motherboard chipset, some of them
bottlenecked below 80MB/s <cough>Via & Sis</cough>.

Embrace the large capacity hard drives available at
affordable prices today.  I've seen 1.5TB drives for $100,
when 10 years ago $100 wouldn't get you 60GB if that.

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