RE: Cheapest way to acheive RAID5 ?

["aashram" <groups@xxxxxxxxxxx>]

I have setup a raid5 using slackware and 2 4bay firewire enclosure.
with software raid5 there is a performance hit. A considerable one.
Something to consider when using as a video server.
In fact in documentation I have read raid5 is not recommended
for large video files, they recommend raid 4.

Either how there is a performance hit. I am still working with mine
to get it working as it should.
I would partition 4 drives to about 100mb or so and play with creating
raids with different settings (chunk etc) and get used to the working
with it.

For linux I used mdadm which is a great little tool and alot more
reliable than raidtools.

I am just about to install slackware or debian on to my dell poweredge
and use that as the fileserver as my pentium III with 512mb ram is
struggling
with raid5 during some actions.


________________________________

From: Hawes,Timothy Edward (GEG) [mailto:haweste@xxxxxxx]
Sent: Thu 14/04/2005 10:00
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Cheapest way to acheive RAID5 ?




Thanks Lee,

I was thinking about common mode failure for drives as I was typing - a
good point to raise.
As you've probably already guessed, I'm not an expert on the subject ;-)
but if a disk fails in a non RAID array do you have to rebuild the array
from scratch, or can you only replace the data which was lost? If it's a
full rebuild I guess that's where RAID pays off - you're back up and
running much quicker and with less interruptions in service.

I suppose the moral is that if you want to keep it, make sure you back
it up :-)

Cheers,

Tim.

> -----Original Message-----
> From: LeeUKHA
>
> Yes, but...
>
> I would start slowly buying drives now from different suppliers...
> ...if you buy a job lot that all came from the same batch the
> likelihood is that they could all fail at the same time (all
> made at the same time from the same components and subjected
> to the same thumps and bumps?)...
> Look back though the archive and you'll see a lot of horror
> stories about multiple drive failure taking entire RAIDs out...
>
> Depending on your paranoia, you can run RAID5 with 'hot
> standbys', drives that are connected but unused and spun
> down, ready to jump in when things start to go wrong...
>
> It's also worth pointing out that DVDR's are only 15p each
> now, and are probably the most indestructible way to back up movies...
>
> Lee
>
> > Lee,
> >
> > Indestructible no, but it should be more resilient?
> Obviously with two
> > disks failing at the same time you're stuffed but you
> shouldn't lose
> > the lot from a single failure, should you?
> > I guess buying n+1 disks initially will then give you an spare
for
> > instant replacement on failure of the first drive and good spares
> > management would mean you'd then buy a new spare to replace the
one
> > you've just installed (and hope you don't get another failure
'til
> > it's delivered).
> >
> > Have I interpreted that right?
> >
> > Cheers,
> >
> > Tim.
> >
> > > -----Original Message-----
> > > From: LeeUKHA
> > >
> > > I think there's some confusion here, just because it's
> RAID5 doesn't
> > > mean it's indestructible...