[mythtv-users] Hard Drive Performance

[Brian Wood]

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 :-)