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).