cvs commit: src/sys/conf Makefile.sun4v files.sun4v options.sun4v src/sys/sun4v/compile .cvsignore src/sys/sun4v/conf DEFAULTS GENERIC GENERIC.hints MAC Makefile NOTES src/sys/sun4v/include _bus.h

[Scott Long]

Doug Ambrisko wrote:
> Kip Macy writes:
> | 
> | The interface is not the same - can one buy an adapter?
> 
> True that technically the interface is not the same.  The SAS connector
> spans the power supply and data port.  SATA has separate data and
> power.  However, the mechanical spacing is the same except the SAS
> drive does not have the gap to fit a separate power cable and separate
> data cable.  I've stuck several SATA drives in a SAS backplane 
> enclosure and Adaptec fan out cable.  The mechanical interface
> precludes a SAS driver plugged into a SATA controller but the
> converse is not true.

The bridge between the two connectors on SAS holds the pins for the
second data channel that SAS supports.  At a pure electrical and
signaling level, the primary channel on SAS is compatible with the
single channel on SATA.  But for many technical and non-technical
reasons, it's possible to plug a SATA disk into a SAS
connector/controller, but not the other way around.

> 
> Do you have a SATA drive to try?  I've even mixed a SAS and SATA
> drives on the same controller at the same time.  I know a few
> people using SATA on a SAS controller since SAS drives are harder
> to come by.

One of the promises of SAS was that you could combine the benefit of SAS
infrastructure (multipathing, channel bonding, and out-of-the-box
connectivity) with the cost effectiveness of SATA.  Of course, that
already existed with Fibre Channel, so the migration to SAS hasn't been
as swift as many had hoped.

> 
> Now Dell doesn't recommend mixing types but I've done it to 
> do some testing.

Even though SATA and SAS are compatible at an electrical level,
there is quite a bit of magic involved in making a SAS controller
talk to a SATA disk.  My guess is that Dell doesn't want you
adding too many magic variables to the mix on such new technology.

> 
> There is no adapter needed :-)
> 
> I wish there was a SCSI drive to SAS interface like PATA drive to
> SATA.  Unfortunately my PATA adapter is not compliant and won't 
> just work with a SAS cable :-(

I suppose that a PATA drive should work on a SAS controller if a SATA
converter is used.  It's also possible to put a Chevy Nova drive train
into an Audi, given enough effort with a welding torch.  I just wouldn't
recommend it.

Scott