"jpk" said:
Many Thanks Alex for this clear answer. Any idea how I could get the SATA
drivers when setting the HDD as a Raid HDD (I have no floppy drive to use
the "F6" procedure) ? Is their a performance advantage in setting my HDD as
a Raid one with the relevant drivers ?
JP
First of all, if you are new to RAID, placing the boot partition
on the RAID array might not be a wise decision. To use RAID, you
really need to understand what to do in an emergency (you go to
use the computer, and receive a "critical" in the BIOS or whatever).
Most people are unwilling to spend the time experimenting with
their RAID array, to understand what procedures to follow, and
the average RAID manual does nothing to help this situation.
There is nothing worse than being unable to boot the computer,
call for help etc, if the RAID breaks.
The back of this manual has a troubleshooting section, and is
one of the few efforts to explain to users, what to do in an
emergency. Versions of the manual for other Southbridges
are also in this FTP tree - but earlier versions contain a less
complete manual:
ICH7 matrix RAID.
ftp://download.intel.com/support/chipsets/imsm/sb/manual50_oem.pdf
RAID 1 is a mirror, intended for reliability. RAID 0 is a stripe,
intended for performance (RAID 0 can use many disks to improve
performance, but motherboard chips typically only support two
disks in a RAID 0 array). If a single drive fails in RAID 0,
your data is lost, making RAID 0 an unfortunate choice for the
boot disk. RAID 1 is safer, as a single failure still leaves the
second disk to boot from. But, if _something_ happens that
damages the contents of both drives, even RAID 1 will not
help - you still need to do regular backups in any case.
And, you may even benefit from using a UPS on the RAID-equipped
computer, as that protects against the power going off in the
middle of an I/O operation (which would cause potential divergence
of the two images).
As for understanding the Intel SATA implementation, try this doc:
http://www.intel.com/design/chipsets/manuals/252671.htm
Basically, what Intel has done is very clever, and they are to
be congratulated for it. In "compatible" mode, a SATA disk
appears with the same hardware characteristics as an old PATA
disk. This makes it possible for an old OS to boot from the
drive, without having to resort to F6 for a driver:
* interrupts via IRQ14 (primary channel) and IRQ15 (secondary channel)
* Command and control block are accessed at fixed I/O locations:
Command Block Offset: 01F0h for primary and 0170h for secondary
Control Block Offset: 03F4h for primary and 0374h for secondary
In Enhanced mode, the SATA drive is moved to the PCI address space.
* interrupt via the INTA# (just like a PCI card)
* Command and control blocks are accessed via I/O space
specified by the following BARs (base address registers)
located by the following PCI configuration offsets:
Offset 10h Primary Command Block Base Address
Offset 14h Primary Control Block Base Address
Offset 18h Secondary Command Block Base Address
Offset 1Ch Secondary Control Block Base Address
Now, in Enhanced mode, I don't know what driver is being used. I
think if you are using a certain minimal Service Pack for your OS,
the driver is built in, but what mode the driver runs in, will
have to be somebody else's guess. (I don't have any SATA
drives to experiment with.)
In any case, AFAIK, the Intel method uses the least amount of
"F6ing", to get your drive working in non-RAID mode. So, be
thankful for small refinements.
On the other side of the coin, Intel's decisions for RAID
functions are a bit more brutal. If you ever want to try
using RAID for the boot disk, you would be well advised to
read the second section here, before doing your OS install.
This "RAID ready" procedure is needed, because there is a
nasty "chicken versus egg" problem, when it comes to drivers
and the RAID setting in the BIOS. The BIOS setting changes
the enumeration of the Southbridge, between ICH5 and ICH5R,
making it impossible to simply install the RAID driver on
top of the current non-RAID driver. (To fix that, it might
means building the array in the BIOS, then do a Repair
Install + F6ing drivers. I don't know if I've read a
successful account of someone doing something like that or
not.)
ftp://download.intel.com/support/chipsets/iaa_raid/IAAR_Quick_Start.pdf
Paul
