[mythtv-users] Hard Drive Performance

[Brian Wood]

On Mar 30, 2006, at 10:33 PM, Martin Bene wrote:

>> Since the OP's hdparm -tT numbers are way low it's obvious he has a
>> problem not related to filesystem, although he might have those
>> troubles as well.
>
>> /dev/hdc:
>>  Timing cached reads:   1392 MB in  2.01 seconds = 692.30 MB/sec
>>  Timing buffered disk reads:  188 MB in  3.00 seconds =  62.63 MB/sec
>> [root at mythtv mythtv]# hdparm -tT /dev/hda
>>
>> /dev/hda:
>>  Timing cached reads:   1368 MB in  2.00 seconds = 683.76 MB/sec
>>  Timing buffered disk reads:  124 MB in  3.02 seconds =  41.12 MB/sec
>
> I don't see any indication of slow harddisks in these numbers -
> "buffered disk reads" are OK.
>
> "cached reads" don't touch the disk hardware or interface at all, this
> is cpu <-> memory bandwidth. Agreed, for a new system the  
> throughput is
> rather pathetic.
>

I had assumed that "cached reads" were reading from the drive's  
internal cache, and would thus use the drives interface, but that was  
only an sssumption.

In any case, hdparm clearly showed that his hda drive was running in  
udma5 mode while the hdc drive was not, most likely due to the latter  
being on the same bus with an optical drive, and this clearly could  
and should be corrected.