Re: SATA HD & DMA ?
From: Rick Moen (rick_at_linuxmafia.com)
Date: Tue, 31 Aug 2004 19:01:27 GMT
The Real Slim Shady <Stan@your.house.com> wrote:
> I know. I was just stating that one could try. Not that it should work.
> As sata is not scsi, perhaps hdparm -d1 should apply.
If your drivers access the disks via the kernel's SCSI layers, as is the
case with libata drivers, 3Ware drivers, and some others, then hdparm
tuning will not work. If you're using a conventional driver/ide-class
or ataraid-class Linux kernel driver, on the other hand, it will.
> All in all, sata is a formidable waste of time and a huge marketing bluff.
Even though I'm a SCSI bigot, I'd call it an incremental improvement
over PATA in every way.
> pata is cheaper and works.
There's no reason SATA shouldn't be cheaper yet, after the inevitable
product introduction period. Current price differences, such as exist,
are a market effect, and will go away.
> sata hardware is still just relabeled pata with an adaptor.
Not always. Early drives were indeed just PATA drives with a Marvell
(or similar) bridge chip. Those are either going away or gone; not sure
which. Moreover, even those garnered some of SATA's advantages, such as
easing of length limits, thinner cables with less impairment of airflow,
> No hotplug....
SATA can in theory do hotplug. A couple of implementations (notably
3Ware) already do their own hotplug, including on Linux.
> no queue command like scsi.
SATA does provide for tagged command queueing. Jeff Garzik is currently
coding TCQ support for his libata driver set, accordingly. It's not
here yet, but will be eventually. (Then, we'll see if it works well.)
> A smaller cable with a different power plug. What a deal.
You also get lower voltage levels (on fully-native SATA drives that
don't use a bridge chip), and consequently lower power levels, which
translates to less heat and the ability to have smaller, quieter
The "150MB/sec" bit (bus transfer speed ceiling) is smoke and mirrors,
because the drives are (as always) bottlenecked on physical read access
times, but could be useful at some distant future point.