[mythtv-users] Laptop Harddrive speed, capacity

Steve Adeff adeffs at gmail.com
Thu Nov 10 10:47:37 EST 2005

On Thursday 10 November 2005 10:08, Brandon Sherman wrote:
> Hullo,
> In my continuing plot to create a MythTV box out of an old laptop, I
> am now eyeing the hard drive.  It is a standard 2.5" drive of unknown
> speed (I'd guess 5400, no more) and 40GB of space.  I'm looking at
> one of these: http://oss.wischip.com/  Which can give me MPEG-2,
> MPEG-4, and DivX.
> Do I need to get another hard drive?  The PlextorX will be connecting
> through a USB 2.0 PCMCIA card, and I'm not sure if a USB 2.0 hard
> disk would be good because of the bus bottleneck issue.
> There  is a 4-pin FireWire port on the computer, but nothing I've
> seen uses it (aside from cameras).
> Any suggestions on the drive?
> Thanks,
> Brandon

Brandon, this sounds like a job for hdparm!
as root run hdparm -I /dev/hd?
replace ? with the drive letter, ie 'hdparm -I /dev/hda'
this will give you a bunch of information on your drive, under the heading 
Capabilities look at the DMA level, it will have an * next to the mode its 
set in, and in theory will only show the DMA levels supported. 
DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
so for instance, this drive is currently set to udma5 (ATA133). I'll assume 
the distro you are using will automatically set the highest level of udma 
support, if not do some googling and use 'man hdparm' and you'll figure out 
how to get it to switch and stay at that level.

now, the REAL information will come from using the 
 -t   perform device read timings
 -T   perform cache read timings
options in hdparm. the important one is '-t' as it will give you a reasonable 
idea as to the max speed the drive can actually write data. 
you'll get an output similar to:
# hdparm -t /dev/hda

 Timing buffered disk reads:   70 MB in  3.05 seconds =  22.95 MB/sec
which is the output from my laptop drive. Write speeds are usually slightly 
faster in buffered writes (~10%) and slightly slower in random writes (~20%).

Don't forget that you'll want to add some overhead considering its both your 
OS drive and your storage drive.

I think the best advice would be to get an external USB2.0 hard drive, you'll 
get the extra space and not have to worry about drive speed issues and you'll 
get some extra space for storing recordings.


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