SATA and SATARAID

Mark,

A brief answer ( or two comments ).

First, as you may know HDD's have only a 16 bit data bus. PCI allows for
32bits. Since we all use LBA addressing we all know that LBA evolved into a
28 bit address. Well 28+16=44 *TILT* it is only a 40 pin connector. Well
it can up two loads to the drive to get to the CHS where the data is
stored.

Contrast that with data coming out serially and addresses and data going in
serially. Information between the SATA controller and the drive is moving at
150mb/s and they have two shielded twisted pair so you can read and write at
the same time.

The bad news is that PCI bus is 4 bytes wide and runs at 33 MHz. I computer
term that a band width of 4*33=132 mB/s. It is not very likely would get
100% of the attention of the PCI bus and the south bridge.

The 2 WD Raptors I have in RAID 0 do 94 mob/so on a sequential read. They
use a Highpoint 1540.

Second point. It looks like we will be living with the connect-the-dots
speed programs for a while. HD Tach and Sandra have timing problems a these
speeds. DiskSpeed 32 really is not flexible enough for RAID work.
PCMark2002 will give you great numbers but even it will report 345mB/s
speeds.

Say Hi to Marge

JPS


..
..