[mythtv-users] How many simultaneous recordings on one drive?

Alex Butcher mythlist at assursys.co.uk
Thu Sep 29 00:46:28 UTC 2011

On Wed, 28 Sep 2011, Richard Morton wrote:

> I am trying to work out why you would configure a system like you have,
> across all those partitions across two very high performance drives, but now
> you are making the heads seek like _crazy_ and that is just for recording,
> add in OS and DB load...

Because I'm using jfs for my recordings filesystems, and jfs filesystems
can't be resized to be smaller. Creating 5x200GB arrays allows me to
repurpose a 200GB array by simply redistributing its recordings amongst the
other 4 arrays (or deleting them!)

> making heads seek
>  - causes most wear on drives and your arrangement must be making the heads
> go mad - constantly.

I usually pre-emptively replace and upgrade my drives at about the 3-4 year
point.  The WD Caviar Black drives have a 5 year warranty.

>  - slows down the throughput as so much time is lost moving the head to the
> right area of the drive
> using multiple partitions means
>  - that when data is being written to two different files in "free" space on
> the drive, if the two files are to be written on two different partitions on
> the same drive the head _has_ to move to a completely different area of the
> disk which takes time.

True. I considered this when I initially set it up, and was prepared to go
back and repartition as a single recordings array if I noticed any
performance problems in operation. I haven't.

In fact, given the low quality of much of British TV, it's rare that I
even record from more than two or three virtual tuners simultaneously.

> I understand the desire to have a reliable system and use RAID1,5,6 or 1+0
> for important and rapidly changing data but this is not usually the case
> with HTPC, there is  some data which changes slowly (ripped videos & music)
> some that you always want to keep (database) and some you can replace
> relatively easily from a backup with no harm (the OS) and then the stuff
> that falls somewhere in that range (tv recordings)
> For instance my setup is much simpler
> 40GB IDE drive for the OS & DB
> 2TB Recordings drive
> 2TB Video music, and general file-server drive

Horses for courses. Storage is cheap, so I've put everything apart from my
local Fedora repo mirror, the 'filler' recordings, /tmp, /var/cache and
/var/tmp on RAID1, thereby pretty much minimising downtime in the event
of a single drive failure.

> R

Best Regards,

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