[ale] RAID, IDE and/or Linux

Denny Chambers dchambers at snapserver.com
Sun Feb 17 23:07:24 EST 2002


I never said it was a great idea, just that it could be done. If David
wanted to use a 3rd HD for offsite disaster recovery, it would be
possible, and cheaper than a lot of your typical backup tape solutions.
If your not talking about much data maybe CD's are the way to go. Anyway
you could set up 3 Hard Drive/Partitions in a mirror. Once they are
setup, and synched, you could shutdown the system, take out the third HD
and take it off site. Once you restart your system, your md device will
show as a degraded raid system, but as Jeff pointed out the third drive
was probably more overhead than anything, therefore your "degraded" md
device would probably operate more efficiently, at least on writes. This
is just once of many possible solutions.

Jeff Hubbs wrote:
> 
> I have yet to see that implemented (RAID 1, not 10 or 0+1).  Even if
> it were, I can only see loss of performance and space efficiency for
> almost no extra benefit.  Yeah, if you couldn't take a performance hit
> upon drive loss or of you need to be able to absorb the loss of more
> than one drive, but really...1:4 space efficiency??  Maybe if I were
> setting up a server in a jungle 200 miles away that can only be gotten
> to with pack mules and a machete...
> 
> - Jeff.
> 
> Denny Chambers wrote:
> 
> > You can setup more than two drives in a RAID1/Mirror. I have
> > actually
> > setup up a 4 way mirror.
> > Keith Hopkins wrote:
> >
> >> David Corbin wrote:
> >>
> >> > I'm contemplating setting up a "big file server" to act as
> >> > storage for
> >> > all my "personal critical data".  This will include source
> >> > control for
> >> > home projects, digital pictures, ripped CDs, digitized audio, and
> >> > perhaps even some video eventually - other stuff too, I'm sure..
> >> > Naturally, the server will run Linux. Because of the great volume
> >> > of
> >> > data that will not be replaceable, I'm contemplating a RAID
> >> > solution.
> >> > This is for "backup and reliability", rather than for "speed".  I
> >> > am not
> >> > so silly to think that this server will survive the rest of my
> >> > life as
> >> > is, however it is my intent that this be a place to be data I
> >> > wish to
> >> > keep the rest of my life.   However, I don't want to spend "lots"
> >> > of
> >> > time administrating it, or doing maintenance every week.
> >> > The question for you folks is, what experiences do you have with
> >> > Linux
> >> > doing RAID, or an IDE RAID controller that I can benefit from?
> >> > One thing I'm concerned about, is what
> >> >  happens when 2 years down the
> >> > road, one drive fails-  First, do I find out about this failure
> >> > immediately.  Second, what if I can't find an exact replacement
> >> > for the
> >> > dead drive.
> >> > There is an implied issue here.  If this data is that important
> >> > to me,
> >> > I'll want to periodically make a copy for offsite.  To me, the
> >> > best way
> >> > to do that these days is on another drive.  Is there a viable
> >> > RAID
> >> > solution that will let me do this?  Can I have "3 equal drives",
> >> > one of
> >> > which is only there occaisionally?
> >> > Thoughts and comments please.
> >> >
> >> If you are going IDE, and wanted the max in safety, I would
> >> suggest using TWO pci-ide controllers (non-RAID, or
> >> RAID0/striping), and use software RAID1/mirroring across them.
> >> That way you can protect yourself and have any easy replacement in
> >> the case of a controller failure.
> >> I've not seen seen any setups of "3 equal drives" in Linux (I have
> >> in HP-UX), but IIRC from reading the md-config docs it doesn't
> >> seem to support more than 2 disks for mirroring.
> >> another note:
> >> http://unthought.net/Software-RAID.HOWTO/
> >> 3.2 Hot Swap
> >> This has been a hot topic on the linux-kernel list for some time.
> >> Although hot swapping of drives is supported to some extent, it is
> >> still not something one can do easily.
> >> Hot-swapping IDE drives
> >> Don't ! IDE doesn't handle hot swapping at all.....
> >> Lost in Tokyo,
> >>    Keith
> >> ---
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