[mythtv-users] New HDD for Mythtv 5400 or 7200 rpm

[Michael T. Dean]

Johnathon Meichtry wrote:

> I agree, if its for a backend go for speed speed speed.  Get the drive 
> with the fastest RPM, the largest cache and fastest interface you can 
> afford e.g. 7200rpm SATA.  If possible get the fastest PCI-X SATA card 
> you can find and you'll break the PCI bottleneck.

IMHO, more gigs are far more important than fast drives.  Spend money on 
space, not on speed.  (Also, RPM's and cache are only two of about 5 
hard drive parameters that are required to determine the hard drive 
performance characteristics)

MPEG-2 streams don't take much bandwidth.  A 10.8Mb/sec stream (the 
maximum allowed by the DVD specification--including audio and video) is 
1,350,000 bytes per second (=1318KiB/sec=1.29MiB/sec).  Since the 
PVR-x50's electronics will hit the quality ceiling far before that kind 
of bandwidth is required, you'll most likely use something like 
4-6Mb/sec for "high-quality" recordings, meaning you'll using at most 
60% of that, or about 0.75MiB/sec.  If you use MPEG-4, you need even 
less bandwidth.

Even for high-definition, bandwidth isn't a problem.  High-definition 
recordings seem to be between 4-10GiB/hr (averaging about 7GiB/hr), so 
taking the worst-case scenario (10GiB/hr), we have 
2982616bytes/sec=2912KiB/sec=2.85MiB/sec.  At this rate, you should be 
able to write several high-def streams concurrently even with "slow" 
hard drives.

Make sure it's UDMA66 or above (and you're unlikely to be able to find a 
new drive today that's not) and that you have an 80-wire IDE cable (if 
using PATA) and you'll be fine.

Mike