[mythtv-users] Opinion on a P4 Backend // HDD Throughput

Tom Dexter digitalaudiorock at gmail.com
Thu Mar 6 16:05:14 UTC 2008


On Thu, Mar 6, 2008 at 12:02 AM, Greg Mitchell <greg at nodecam.com> wrote:
> Josh White wrote:
>
>  > I agree completely with the separation of the recordings and the
>  > database to separate physical drives.  I got lucky when I set my system
>  > up, and did that by accident.  I guess I just assume that's how everyone
>  > does it (bad assumption).
>
>  I started out with a single 200G drive for my entire system - I set up
>  two LVMs, one for my system and one for recordings.  The recordings LVM
>  got added to with another 200G and a 300G drive over time, but
>  essentially they were still sharing the same drive because of my
>  stupidity in how I initially set it up.
>
>  And for SD, it was fine - just when I got into HD stuff that I started
>  really having IO problems which caused ivtv to go haywire.
>
>
>
>  Greg
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>
When I setup my Dell 4600 backend I wanted a lot of storage for OTA
HD.  I put in two 500GB Seagate IDE drives with most of both used for
a big LVM partition for recordings.  That of course meant that the OS,
database, logs etc are in fact sharing the primary drive with part of
the LVM partition.  At that time, I wasn't aware that that's not a
good idea.  I'm not sure what else I could have done in order to have
that much storage in the machine though.  I don't think that thing
will physically fit three drives even if I could use sata along with
the IDE drives.

Bearing in mind that I have only one frontend and don't do any
commercial skipping or the like on the backend, it works perfectly
with three HD-5500 cards all recording HD at the same time while a
forth previously recorded show is being watched by the frontend.
Interestingly, the machine has only 512 MB of ram.

On rare occasions I get IOBOUND errors in the backend logs, but oddly
enough, they _never_ occur during heavy recording.  They always seem
to happen when nothing's going on except live TV on the frontend.
I've never figured that out, but I've also never seen any visible
issues as a result.

Tom


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