[mythtv-users] Config suggestions for powerful MythTV Backend

[James Robertson]

> OK, my first suggestion is to ditch the PERC controller - it's a pain to use
> in Debian. You can set it up without any OS support, but you'll have zero
> visibility without installing the appropriate software. Dell don't support
> anything but RedHat, and I've had "mixed" results trying to get their
> software to work. I now have most of my machines with the controller in JBOD
> mode and use MD for raid - but the controller still gets in the way of
> accessing SMART data.
>
> OS. I'd suggest a RAID1 partition across at least 2 disks for a /boot
> volume. The trick here is that the boot volume can be accessed from any of
> the member disks by the BIOS without needing any raid software loaded. Thus
> it's possible to boot the system from a raid volume before the raid software
> is loaded to access it !
> Then I'd put the OS on at least two disks (RAID1 again). I tend to use a
> native partition/array for the OS itself (ie /), and then LVM to manage the
> rest (eg /var). That means the root filesystem is available even if your
> recovery disk doesn't have LVM on it. Not the only way to do it, just my
> preference.
>
> That will leave you well in excess of 100G free on each of the OS disks to
> use for storage. Having the OS on the same disks as storage won't be an
> issue - with your RAM, all the regularly accessed stuff will stay in RAM
> anyway. On my home Myth system (small HP Microserver), I have two SATA
> disks, with the OS & Database across them (RAID1) and storage using the
> remaining space - it's not been an issue even with 5 recordings going (two
> DVB tuners, UK Freeview, Multirec) + commflagging + one playback stream.
>
> If you use the remaining space on the OS/database disks for "read only"
> storage (ie videos and music) it will be less of a potential problem than it
> might be for TV recordings.
>
> As for recordings, if you don't mind about redundancy, do not use RAID 0.
> Use separate disks and add a directory on each of them to a storage group -
> eg if you used all 6 disks, then you'd have 6 directories listed in your
> default storage group. If you use multiple storage groups, then you can
> split the directories between them. Apart from performance, if one disk in a
> RAID 0 set fails, you lose the lot, if one disk in a set of 6 separate
> drives fails, you lose just what's on that disk.
> Myth will default to spreading the recording load between disks, and with
> only one tuner card, you are never going to get close to saturating any of
> the disks.
> With RAID 0 (striping), you will be writing all the concurrent recordings
> across the whole array and it's pot luck whether individual recording
> streams will hit the same or different disks at any point in time.
>
> If you do want redundancy, then consider 3x 2 disk RAID1 arrays, so you have
> 3 directories to put in your storage groups.
>
> --
> Simon Hobson

Wow!  Some great advice here, thanks so much Simon!  I will be
digesting this and doing more research based on your suggestions, I''
be sure to let you know how I get on.  Thanks again for taking the
time to respond, it is very much appreciated.

James.