RE: Cheapest way to acheive RAID5 ?

["Phil Harris" <phil@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.

Interesting comments there ... I'm running software RAID5 under Fedora Core
3 and although there is a performance hit over writing directly to a single
drive or a striped RAID0 array (26mbytes/sec on a single drive or RAID0
versus 17mbytes/sec on RAID5) it doesn't seem to have any bearing on the
arrays ability to serve up a reasonable amount of movies simultaneously.
I'm
using a 2.4GHz Athlon with 512Mb RAM and that also handles HomeVision
(using
Schelte Bron's Linux HV software) as well as being planned to handle FTP
and
TFTP / DHCP etc.

I'm using 2 x 8 bay firewire enclosures with 16 x 160Gb drives set up as
two
8 x 160Gb drive RAID5 arrays. I had considered using it as a single array
but I decided against it as then I can keep each enclosure a viable entity
in its own right.

I've already had two drives fail (not at the same time of course) and even
whilst rebuilding the array (which takes about 12 hours) it's still more
than quick enough to serve up movies (note the plural). In fact the only
time I've had any stuttering in playback from the arrays has been when I
was
playing back two movies from the array whilst simultaneously also copying
about 200Gb of movies *UP* to the array from my "ripping"
machine.

Phil