Nick Piggin wrote:
>>
>> Any good SCSI drive knows the physical geometry of the disk and can
>> therefore optimally schedule reads and writes. Although necessary features,
>> like read queueing, are also available in the current SATA spec, I'm not
>> sure most drives will implement it, at least not very well.
>>
> The "continuous" nature of drive addressing means that the kernel
> can do a fine job seek-wise. Due to write caches and read track
> buffers, rotational scheduling (which could be done if we knew
> geometry) would provide too little gain for the complexity. I would
> say that for most workloads you wouldn't see any difference. (IMO)
OTOH you can come up with scenarios like, say, a DBMS doing 16K page
aligned IO to raw devices where you might see big gains from making sure
those 16K chunks didn't cross a physical cylinder boundary.
-- Chuck - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue Apr 15 2003 - 22:00:29 EST