[mythtv-users] RAID5 ATA IDE hardware card recommendations formythbackend machine

[Dave Howorth]

Yan-Fa Li wrote:
>>> Think of an old fashioned 78RPM record player.  The disc spins at
>>> a constant speed, 78RPM.  The outer part of the disc is moving
>>> faster than the inner part, but the time the head has to read and
>>> write is the same regardless of where you are on the disc.
>>> Therefore the inner part gets data faster because it has to spin
>>> much less to read the same amount of data assuming all the tracks
>>> hold exactly the same amount.

Hi Yan-Fa

As John Andersen said, this is no longer true. The tracks *don't* hold 
the same amount and it's the outer part of the disk that gets data faster.

> http://www.ntfs.com/hard-disk-basics.htm

That page appears to describe how disks worked some years ago.

Try this one for a different explanation that I believe describes 
current disks:
<http://www.dewassoc.com/kbase/hard_drives/hard_disk_sector_structures.htm>
'Zoned recording' is the important difference.

> /dev/md1: Timing buffered disk reads:  136 MB in  3.01 seconds =
> 45.18 MB/sec

The figures above are for the outside of the disk, those below for the 
inside.

> /dev/md4: Timing buffered disk reads:   98 MB in  3.01 seconds =
> 32.56 MB/sec

Cheers, Dave