Subject: Re: UVM/other problems for desktop users in current?
To: Daniel Carosone <firstname.lastname@example.org>
From: Oleg Polyanski <Oleg.Polianski@team.telstraclear.co.nz>
Date: 12/19/2002 15:21:02
>>>>> "Daniel" == Daniel Carosone writes:
>> Yep. And I'd appreciate it if someone explained _why_ decent
>> IDE with DMA is so bad when compared to SCSI. Especially if you
>> only have one device per port and the raw sustained performance
>> is 30 MB/s or more with only a little CPU loading.
Daniel> The main reason is that there's only one outstanding
Daniel> operation to the disk at once. SCSI disks, with tagged
Daniel> queueing, allow multiple outstanding requests, that the
Daniel> drive can respond to in the order that best suits its
Daniel> internal state (disk head position, mostly).
This isn't true, most modern IDE hard drive have the tagged