On Wed, 26 Apr 2000, Daniel Roesen wrote:
Clue: this is the way every RAID controller I know of works these days.
???????? what??? Do you know what are you are talking about????? hey,
i've got some $1000 raid cards for you. (my markup is $980).
a REAL raid controller is a *complete computer* with onboard
CPU (eg StrongARM SA100 on the ExtremeRAID, Intel i960 on the
DAC960's, AMD 29k on the older Compaq SMART-2's.*) It has a ROM to
store it's software and RAM for runtime needs of the software and for
caching, along with 1 or more SCSI host adapters and a PCI bridge all
connected by a host bus. Ie it's a full-blown computer!
On a real hardware RAID controller the software runs on the CPU
embedded on the card.
The Promise on the other hand has NO onboard CPU. The RAID facilities
are provided by X86 code sitting on the ROM which is *called by the
BIOS*, and therefore runs on the host CPU.
Ie with the Promise RAID card the RAID software is running ON YOUR
Pentium/K6/whatever CPU under control of the BIOS.
PS: Linux doesn't use BIOS to access devices.
*Did i say it did????*
In fact this is precisely why the promise raid can't be used under
linux. (and why it's also difficult under NT).
Hardware wise the card is JUST AN IDE CONTROLLER!
So don't bother Promise for RAID drivers --- cause linux already has
them: ie Promise IDE driver + software RAID.
--
Paul Jakma [EMAIL PROTECTED]
PGP5 key: http://www.clubi.ie/jakma/publickey.txt
-------------------------------------------
Fortune:
Real programmers don't bring brown-bag lunches. If the vending machine
doesn't sell it, they don't eat it. Vending machines don't sell quiche.
*note that gcc can compile code for all these CPU's. Heck linux even
runs on StrongARMS so in theory you could port linux to a Mylex RAID
card. ie a Linux/DAC1164 port.
