[mythtv-users] Two-backends with two-frontends on one machine?

[Billy Macdonald]

On 7/11/07, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 07/11/2007 11:27 AM, Steven Adeff wrote:
> > 1) RAID 1 seems like overkill, why not go with RAID5? I've got a 6
> > drive RAID 5 device that keeps up with my 4 HD tuner backend with two
> > HD capable frontends no problem.
>
> And, in the future (i.e. 0.21 and up), RAID may in fact work against
> you.  With Storage Groups, you can set up your system to write each
> recording to a separate disk (provided enough disks), thereby
> significantly reducing fragmentation and seek issues.  I have 4 HDTV
> capture cards and more drives than capture cards and have configured
> Myth so that it will only write two shows to the same disk if that's the
> only way to record the show (i.e. if all the other disks are full).
> After using it this way for some time, I can say I'll never use a
> multiple-disk (RAID or LVM with multiple physical volumes) configuration
> with Myth again.

RAID 1&5 provide redundancy that I don't think your solutions
addresses.  Your solution seems to be solving more of a problem that
isn't there IMO.  I have 4 HDtuners, and 3 pvr250's.  All 7 tuners can
record to my LVM volume (not striped, 3 disks) and I can play back an
HD recording at the same time.  And these are cheap IDE drives that I
got on sale at Best Buy.  Now being able to store recordings in more
than one location does provide flexibility which I believe is a good
thing.  But I'm not sure it's really needed for performance.

And this past weekend I learned to really like LVM.  I mistakenly made
my storage partition reiserFS, which I see in the docs is not good for
myth.  I was able to shrink my filesystem, shrink the lvm volume,
create a new volume, move some files, shrink, grow, copy, shrink,
grow, copy until all the files were moved to the new filesystem where
the old filesystem once lived.  All in all, pretty cool I thought.

Billy

>
> (Granted, with N capture cards and N or more RAID's, you can get the
> same reduction in fragmentation and seek issues, but, really?)
>
> > I can see your point about hardware failure (motherboard, CPU, RAM,
> > etc) with a single machine though. I think its a rare enough
> > occurrence though that perhaps having spare parts on hand may make
> > more sense if your that worried.
> >
>
> And, if using a single system with master/slave backends and the master
> fails, it's easy enough to "promote" the slave to a master (assuming
> availability of the DB or a DB backup) while getting parts to fix the
> broken system.  And, while the recordings on the broken system are not
> available, you just can't watch them (and Myth won't have issues with
> their non-availability).
>
> Mike
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>