Thread: IDE RAID
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Old September 19th 04, 04:19 AM
Ron Reaugh
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"Leythos" wrote in message
...
In article ,
says...

"Leythos" wrote in message
...
In article

,
says...
All [S]ATA RAID is software/firmware RAID except fancy/expensive

cards
like
3Ware and top Promise cards. I know of NO onmobo HW [S]ATA

RAID...it's
all
software/firmware.

ASUS PC-DL Deluxe has both Intel RAID 0/1 SATA controller and Promise
RAID 0/1 Controller (This is the better of the two).


BOTH are software/firmware RAID and not HW RAID however.


The firmware handles the RAID completely on the Promise controller,


Right, that firmware is x86 code contained in the mobo's BIOS just like the
Intel RAID firmware inside that same mobo BIOS.

the
software is just a driver,


Right, just like firmware is a driver...both are x86 code executed on the
host's x86 CPU.

That Promise firmware and Intel firmware are used ONLY during POST. After
that in an OS like XP ALL activity with both the Promise and Intel RAID are
handled by OS x86 drivers.

like the IDE, ATAPI, SCSI, etc... drivers you
need on other motherboards or that are included with the OS.


Right.

Don't kid
yourself, the only thing that would make the RAID any better is if it
included a slot on the MB for cache.


HUH?

Hardware RAID is completely different. By definition HW RAID offloads all
RAID processing to the RAID card like a 3Ware. All RAID 5 parity calcs are
done on the RAID card by its own resident RISC CPU.

In RAID 1(mirroring) the data gets written to each drive(two identical
redundant writes). In software/firmware RAID 1 like Promise/Intel that data
moves over the hosts I/O bus structure TWICE for the two writes and that's
done by TWO cycles through the host's x86 driver code. In HW RAID that
write data goes over the host's I/O bus structure just ONCE and the host's
x86 driver code deals with that data just once. The HW RAID card then does
the two writes to the two RAID 1 drives using its onboard RISC CPU.

In RAID 0(striping) the host's CPU driver does all the stripe cutting
calculations and then divies the data to be written/read to the individual
drives. In HW RAID all that is done onboard the RAID card by its RISC CPU.

HW RAID always makes the whole array look like a single HD to the PC from
POST time through the OS load and operation.

The following Promise cards are software/firmware RAID:
FastTrak TX2200
FastTrak TX4200
Inexpensive RAID cards like Highpoint and SIIG are also all
firmware/software RAID and all are $100..

Really neat SATA HW RAID cards a
http://www.3ware.com/products/serial_ata9000.asp
They cost $350 and up. They however offer little advantage for RAID 0 and
RAID 1 as that extra x86 processing is minimal for RAID 0 and RAID 1. RAID
5 is a whole different ball game and is where these 3Ware gadgets shine.
Also that is why there is little advantage in using the mobo's RAID for W2K3
or W2K as these OS's offer great RAID 1 support in the OS.

The Promise chip on the mobo is nothing more than a fancy ATA controller
chip with NO significant RAID functionality on it. All on mobo Promise RAID
is firmware/software in x86 code hosted by the host's x86 CPU.