Unmapped buffers: to be merged in several days

[Matthew Jacob]

On 3/11/2013 3:22 PM, Jim Harris wrote:
> On Mon, Mar 11, 2013 at 2:11 PM, Konstantin Belousov <kostikbel at gmail.com>wrote:
>
>> FWIW, I tried to get an Intel documentation for IOAT engine which should
>> allow to perform the XOR checksumming of the unmapped buffers, suitable
>> for e.g. hardware-assisted software raid5, but did not succeeded.
>>
> Please note that XOR checksumming support only exists in the
> E5-1600/2400/2600/4600 series (Sandy Bridge Xeon) and C5500/C3500 series
> (Jasper Forest - based on Nehalem Xeon) processors.  The SNB Xeon series
>
It's been our experience at Xyratex that the h/w XOR checksum engine is 
generally slower than the CPU, at least with more modern Sandy Bridge 
chipsets. But, as you know, YMMV.