On Sat, 2005-06-25 at 21:29 +0000, Mark Weaver wrote:
> according to Broadcom the bc4852 is indeed hardware RAID. we've been
> attempting to get this going with their Linux drivers, but keep getting
> stuck at the point where the Linux installation hangs loading the driver.
Ahhh, no. From their own marketing materials on the RAIDCore ...
"Fulcrum Architecture
Platform-independent RAID *SOFTWARE* architecture"
"XcelCore Software
RAID *SOFTWARE* stack providing highly integrated storage subsystem"
Now they put together some interesting, 4-8 channel cards. The design
is to maximize throughout to a set of 4-8 ATA channels. But they
feature *0* "intelligence" on the card itself -- *0* memory (other than
a little extra SRAM buffer in the ATA channels). They are 100% driven
by the host (i.e., the main CPU).
The "software" is designed around the ATA channel setup, and Broadcom
offers extensive features (and charges piecemeal for them). These
software features can actually offer more RAID levels, rebuild/resize,
etc... options than most "intelligent" RAID cards. But they are still
driven by the main CPU.
When the RAIDCores first came out, they were pretty impressive in the
benchmarks -- until you looked at the benchmarks. I.e., 100% _read_
RAID-5 benchmarks because RAID-5 is basically just a RAID-0 when
reading. When you are writing data to a RAIDCore RAID-5, or rebuilding
it, the performance is absolutely horrendous because your system
interconnect is busy pushing _all_ data through the CPU (the actual XOR
operation is not the problem).
--
Bryan J. Smith b.j.smith@xxxxxxxx
---------------------------------------------------------------------
It is mathematically impossible for someone who makes more than you
to be anything but richer than you. Any tax rate that penalizes them
will also penalize you similarly (to those below you, and then below
them). Linear algebra, let alone differential calculus or even ele-
mentary concepts of limits, is mutually exclusive with US journalism.
So forget even attempting to explain how tax cuts work. ;->
