[CentOS] how do export a block device via eSATA?

[Robert Heller]

At Sun, 13 Feb 2011 11:00:39 -0800 CentOS mailing list <centos at centos.org> wrote:

> 
> On 02/13/11 10:53 AM, Rudi Ahlers wrote:
> > Does any one know how to, if at all possible currently, to export a
> > block device via eSATA? i.e. how do I do something like iSCSI, but
> > over eSATA?
> >
> > I have a cheat ($15 probably?)  media player at home (Egreat EG-M31B
> > Network Media Tank - awesome little machine) that runs some flavor of
> > Debian and can be connected to any PC via eSATA as an external HDD's.
> > i.e. it exports the built-in HDD as a block device to the host (My
> > laptop or PC).
> >
> > Now, the question is, how can I do this on Linux?
> > Would I need a different eSATA card than the on-board eSATA port on
> > most motherboards? Or would the on-board one work?
> 
> I suspect your media tank is doing something electrical, like idling its 
> processor, and re-routing the sata port directly to the internal storage 
> device, when its in this mode.   I'm unaware of any SATA target drivers 
> (as opposed to the normal initiator drivers in libata etc)

More likely, it is running some custom software the connects to the
exposed port (which is probably not a typical PC SATA port -- it would
be wired like a Hard Drive's SATA connector (opposite gender, opposite
signal directions, etc.).  The custom software presents itself on this
port like it was a hard drive and implements some sort of logical hard
drive based on the actual internal hard drive -- not really much
different from a USB connected mp3 player or camera -- the USB
connected mp3 players / camera are just using a different physical
interface (USB), but the logic is the same. Again, the USB port on
these devices is 'wired' the opposite from the USB port on a normal PC
and the logic behind it is also opposite (you cannot really connect a
USB port of one PC to the USB port of another -- there is no such thing
as a USB 'cross over' (Ethernet) or null-modem (RS232) cable in the USB
(or firewire) world). The processor in the little box is implementing
much that same sort of processing that goes on inside the micro
processor on the controller board of a hard drive -- modern hard drive
controller boards are really a full fledged little computer running a
very special program that implements the drive end of the mass storage
interface (SCSI, SATA, PATA, etc.).  The media tank is just taking this
to a different level.

> 
> 
> 
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Robert Heller             -- 978-544-6933 / heller at deepsoft.com
Deepwoods Software        -- http://www.deepsoft.com/
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