Raid ain't just one thing.  Raid referes to the cheap physical media, how
that media is used logically is where raid makes sense.  There are several
levels for different purposes.  Here are a few that home users *may* desire
to use for critical data.

Data mirroring
uses 2 identical drives and stores everything on both drives, if one fails
the monitoring software just gets data from the good one (and alerts the
user about the failed drive).  Good security, no speed gain, twice the cost.

Data striping
breaks each byte into smaller units and stores part of each byte on a
different drive *at the same time*. Typically 3 drives are used, although
you *can* get away with just 2.  Good security, good speed gain, only
slightly more expensive as all of the storage space is used with no doubling
up like in mirroring.

Data striping with Raid level 2
uses 2 or 3 cheap, identical disk drives to store part of each data block
over the (2 or 3) drives along with a mathematical description of the rest
of the data block (stored on the other drives).  If a drive fails the
software can re-construct the 'missing' information from the remaining data
and the math formula (a little slower than from the striped drives, *but* it
does get the *lost* data back).  Excellent security, good speed gain, only a
little more expensive than simple striping.

Mirrored level 2 striping
 is for the ultra paranoid.

There are other security models used too, but these are the main application
for raid stacks.

Bye.

        -----Original Message-----
        From:   root [SMTP:root@PROF.PMMF.HU]
        Sent:   Wednesday, 18 August 1999 17:03
        To:     PICLIST@MITVMA.MIT.EDU
        Subject:        Re: [OT] Linux versions?

        On Tue, 17 Aug 1999, Paul B. Webster VK2BZC wrote:

        > John Griessen wrote:
        >
        > > How to partition your HDD is not covered very well in the how
to's...
        > > I'm still confused about that, but since I am going to be just
        > > using a station as an X terminal, I don't care enough to go
beyond
        > > a vanilla installation yet.
        >
        >   I'm *NO* expert and haven't figured out what a RAID array is
yet, but
        > partitioning seems simple.
        >
         --- snip ---

        A RAID array is AFAIK a huge array of hard disks and it is a
        fault-tolerant device used mainly in mission-critical server
applications.
        A normal desktop user won't meet it directly.

        I hope this helps.

        Imre

        PS: It is only mentioned bcus Linux supports also RAID as it used on
the
        said area.