[Pc_Support] 320GB WD3200JD SATA drive for $107 shipped ...

[Bryan J. Smith]

Jason Boxman <jasonb at edseek.com> wrote:
> How so?

Logical guess based on semiconductor exposure.

While ASIC+SRAM is the absolute best approach for
non-blocking, cached I/O, it is not the same for buffered
I/O.   It's very likely that 3Ware was finding it's ASIC was
coming up short as a general I/O Processor, so they added an
embedded PowerPC.

It's like trying to use a switch fabric as a [real] router. 
You need to add extra brains and buffering to make a switch
fabric into a layer-3 switch.  Merely adding DRAM for
additional buffer wasn't cutting it.

> I know of one person who was using the 9500-S and
> found it wasn't delivering the RAID 5 performance they
> were looking for. 

There were a few bugs in a few 9500S firmware releases that
hurt RAID-5 performance.  3Ware has solved pretty much all of
them, but I don't think adding DRAM to their ASIC engine was
going to get the kind of performance they should expect.

> Is it because the 9550 is PowerPC based that indicates
> the ASIC+SRAM+DRAM wasn't enough?

It's more like the embedded PowerPC+DRAM combination was far
better for RAID-5, but there still appears to be their
ASIC+SRAM combination for non-blocking I/O.  E.g., when doing
any Reads (even from RAID-5), as well as RAID-0, 1 or 10
writes.

Best of all worlds, for about the same price as the 9500S
series.


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