Questions on relative target ports
burn at goldweb.com.au
Wed Mar 3 13:08:00 PST 2004
* From the T10 Reflector (t10 at t10.org), posted by:
* Burn Alting <burn at goldweb.com.au>
On Thu, 2004-03-04 at 03:21, Elliott, Robert (Server Storage) wrote:
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Elliott, Robert (Server Storage)" <elliott at hp.com>
> > -----Original Message-----
> > From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf
> > Of Burn Alting
> > Sent: Tuesday, March 02, 2004 5:11 PM
> > Subject: Questions on relative target ports
> > I am doing some work on raids and have some questions on
> > Relative Target Ports.
> > Let's say I have a raid enclosure with two controllers, each of which
> > has two host ports. I can configure a "data set of disks" to
> > present on one or more of the controllers and their host ports.
> > Now my question is:- Is a 'relative target port identifier'
> > a. with reference to the hardware (ie controller 0 port 0 == 0x01,
> > controller 0 port 1 == 0x02, controller 1 port 0 == 0x03 and
> > controller 1 port 1 == 0x03)
> > OR
> > b. with reference to the data set (ie if the data set is
> > presented only on controller 1, port 1, then the relative target
> > port identifier will be 0x01; alternately if it where on both
> > host ports on controller 1, then port 0 would be 0x00 and
> > port 1 would be 0x01).
> > Thanks in advance
> > --
> > Burn Alting <burn at goldweb.com.au>
> I'm not sure what you mean by "data set of disks." SCSI defines
> logical units, target ports, and target devices.
> If there are 4 target ports providing access to the logical unit
> (they're all in the same target device), they could be numbered:
> controller 0 port 0: relative port identifier 1
> controller 0 port 1: relative port identifier 2
> controller 1 port 0: relative port identifier 3
> controller 1 port 1: relative port identifier 4
> If some logical units are only accessible through some target
> ports due to configuration (e.g. the Access Controls commands),
> the relative port identifiers should still be consistent.
> Relative port 1 should refer to the same target port, regardless
> of which logical unit is being accessed.
> If certain logical units are only accessible through certain
> target ports forever, then they might need to be considered
> as being in two separate SCSI target devices.
> Rob Elliott, elliott at hp.com
> Hewlett-Packard Industry Standard Server Storage Advanced Technology
Thanks for your e-mails.
Sorry for the poor terminology, what I meant by 'data set of disks' is a
set of disks which can be presented as a logical unit on one or more
physical ports which could have differing scsi id's and scsi luns.
Let's say I have two logical units A and B and my two port, dual
controller raid setup. Unit A is presented on
Controller 0, port 0 as SCSI ID 0, LUN 0
Controller 0, port 1 as SCSI ID 1, LUN 0
Controller 1, port 0 as SCSI ID 0, LUN 0
Controller 1, port 1 as SCSI ID 2, LUN 0
Unit B is presented on
Controller 0, port 0 as SCSI ID 0, LUN 1
Controller 1, port 1 as SCSI ID 2, LUN 1
For logical unit A, the relative port numbers would be 1, 2, 3 and 4 - a
My question was essentially, what do I do about logical unit B. Since it
is only ever "dual-ported", should it only have relative port numbers as
1 and 2, even though another logical unit presents different portnumbers
on the same physical bus although a different lun?
Burn Alting <burn at goldweb.com.au>
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