[mythtv-users] Hard Drive Performance

[Calvin Harrigan]

Brian Wood wrote:

>On Mar 31, 2006, at 6:34 AM, Wander Winkelhorst wrote:
>
>  
>
>>On 3/31/06, Brian Wood <beww at beww.org> wrote:
>>    
>>
>>>On Mar 30, 2006, at 10:33 PM, Martin Bene wrote:
>>>
>>>      
>>>
>>>>>g 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.
>>>      
>>>
>>Well, ATA133 (The fastest parralel ATA to date) has only a maximum
>>throughput of 133 megabyte/sec, so there is no way you can do 683.76
>>MB/sec
>>
>>Optical drives and hard discs can share a ATA bus without any slowdown
>>at all. The optical won't limit the hard disc to ATA33.
>>
>>What will cause problems is using a 40 wire ATA cable instead of a 80
>>wire one. That WILL limit you to 33MB/sec speeds.
>>
>>Allso, ATA is a 1 device-at-a-time protocol, so keep the devices that
>>you use the most at the same time on seperate busses.
>>So don't put the CDROM and the harddisc you are ripping to on the same
>>bus, and dont put the two hard discs on the same bus either
>>
>>For best performance, buy each device (HD, CDROM, DVD, whatever)  
>>it's own bus.
>>
>>    
>>
>
>I never really came to like the IDE interfaces. It seemed at one  
>point many years ago that the PC world was moving in the correct  
>direction, towards SCSI, but then some joker, trying to save money no  
>doubt, came up with all the "UDMA" interfaces, which claim great  
>speeds but somehow can never achieve them, sort of like USB-2.0.
>
>Since you appear to know more about these interfaces than I do,  
>perhaps you can answer a question that has always bothered me:
>
>It is quite obvious that the IDE connector on the motherboard has 40  
>pins, as do the connectors on the drives.
>
>So what is with an 80-conductor cable ??
>
>I know that along with the 80-C cables came faster speeds and "cable  
>select" for device strapping, but what are all those extra wires  
>connected to and how does that make for faster speeds ??
>
>Sorry if this is a dumb question but I am still more or less stuck in  
>SCSI-Land, a real "Man's" interface :-)
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>  
>
The extra lines/pins are used as shield and are so grounded.  It helps 
with crosstalk and noise.

Calvin...