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Re: Proliant CSB-6 Raid Drivers for Fedora

On Sat, Nov 06, 2004 at 09:19:15AM -0500, AWC Maillists wrote:
> installed onto lower-end motherboards.  By what you are saying it sounds 
> like these "RAID" controllers are kind of like Winmodems... offloading 
> the real work to the CPU and OS.  Or am I still not getting this right??

That would be overqualifying them.

There are really three kinds of raid floating around.

The first is pure software raid like the CSB6 raid, the ICH-R, most promise
PATA controllers and so on. These have no hardware assistance for raid at all
just a different BIOS (and often price). Almost every parallel ATA RAID
falls into this (Some exceptions eg 3WARE and IT8212)

The traditional hardware raid controllers do all the raid in hardware or
onboard processors - these range for simple devices like the 3Ware which
is fast but basic to the aacraid which has full hardware logical volume
management, live migration and the like. They can help if your PCI bus is
the bottleneck or with raid5 but many of them underperform software raid
(Intel make very good raid controllers called "Pentiumn IV" and a CPU upgrade 
is suprisingly cost effective as is SMP)

What are starting to appear now (although its an old idea one one the
old Adaptec AAC-1xx cards did) are hybrid cards which do some things in
hardware (such as XOR and buffering to keep PCI transfers down to one per IO)
but do the rest in software - these are more akin to the "winmodem" world than
perhaps the pure software raid. [although some winmodems are also awfully
dumb too]


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