non-RAID SATA

[Erik Trulsson]

On Sun, May 25, 2008 at 08:01:42PM -0700, Ted Mittelstaedt wrote:
> 
> 
> > -----Original Message-----
> > From: owner-freebsd-questions at freebsd.org
> > [mailto:owner-freebsd-questions at freebsd.org]On Behalf Of
> > perryh at pluto.rain.com
> > Sent: Sunday, May 25, 2008 6:11 PM
> > To: freebsd-questions at freebsd.org
> > Subject: non-RAID SATA
> > 
> > 
> > I am looking for a cost-effective way to add a SATA drive to an
> > existing 7.0 system whose on-board controller is PATA, and am not
> > getting very far at all in identifying an inexpensive controller
> > which would be expected to work well.  (I'd prefer PCI, since the
> > USB in this box is probably 1.0 and not capable of sustaining
> > desirable data rates.)
> > 
> 
> SATA is faster than PCI.  Most people would replace the motherboard
> or use a USB 2.0 card which has a far faster transfer speed than
> PCI does as a transition, with the expectation that sooner or
> later they are going to replace the system.

While it is true that the maximum theoretical transfer speed available
from SATA (150MB/s or 300MB/s depending on SATA version) exceeds that
of a normal PCI bus (133MB/s for a standard 32bit/33MHz bus), there
is currently no single SATA disk available on the market that will
swamp the PCI bus.
USB 2.0 is however much slower than either of SATA and PCI.
USB 2.0 has a maximum theoretical transfer speed of 480Mbit/s ( = 60MB/s)
with a practical maximum of maybe 30-40 MB/s - less than half of either PCI
or SATA.


> 
> > All mentions of SATA in the hardware guide and FAQ seem to be of
> > RAID controllers, or else too generic to guide a choice of add-in
> > cards.
> > 
> > Does anyone have any experience with this that they would be
> > inclined to share?
> 
> In automotive terms your adding a free-flow exhaust to a restricted
> engine - in the trade we call them adding a "fart can" because
> they do nothing to help the car go faster since there's restrictions
> further up the chain.

It is unlikely that a PCI-based SATA card would be a noticable bottleneck
in this case unless one were to connect several high-speed disks to the
card.

> 
> Go buy an inexpensive USB 2.0 external disk case, then buy your
> SATA disk and stick it inside of that, with the idea that eventually
> your going to get a faster machine you might be able to use the disk in.

USB however would be a quite noticable bottleneck.  Bad idea if you want
anything resembling speed.



-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se