SCSI device names

Elliott, Robert (Server Storage) Elliott at hp.com
Tue Oct 22 17:23:31 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
This is a multi-part message in MIME format.

------_=_NextPart_001_01C27A2A.6A96E265
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable

The current rule in SAM-3 is that a device may have one device name per
transport protocol.  This means, for example, that a target device with
both SAS and iSCSI target ports has two device names - the iSCSI name
and the SAS device name.

Assuming 02-254 (WWNs for W-LUNs) passes, these would be returned as =
two
device identifiers in VPD data:=20
1. SAS device name=20
association=3Dtarget device (2h)=20
protocol identifier=3DSAS (6h)=20
identifier type=3DNAA (3h) =20
identifier=3DIEEE Registered format (NAA=3D5h), 8 bytes long=20

2. iSCSI device name=20
association=3Dtarget device (2h)=20
protocol identifier=3DiSCSI (5h)=20
identifier type=3DiSCSI name-based (7h)    (to be proposed in 02-419)=20
identifier=3DUTF-8 format string, up to 224 bytes long=20

It would be simpler if there were only one device name for a device.=20

Since only iSCSI has defined device names to date (SAS is just planning
to include a device name now, and FCP-3 might define one too), we have
an opportunity to make all device names follow the iSCSI name-based
format and let each device have a single device name regardless of
protocol. =20

The iSCSI name format is a UTF-8 (similar to ASCII) string that starts
with a naming authority:=20
"iqn."  for an iSCSI-defined reverse domain name string (e.g.
"iqn.2001-04.com.acme:storage.disk2.sys1.xyz")=20
"eui."  for a hexadecimal representation of an EUI-64 identifier (e.g.
"eui.02004567A425678D")=20

iSCSI could easily add an "naa." type to carry a hexadecimal
representation of an NAA identifier (e.g. "naa.52004567A425678D"),
needed to carry the format used by SAS and Fibre Channel port names.

Then, a target device with target ports of different protocols could =
use
any string format it likes as its sole device name.=20

Likely choices:=20
iSCSI-only device: "iqn." (it may have no hardware names available)=20
SAS-only device: "naa."=20
FC-only device: "naa."=20
SRP-only device: "eui."=20
SBP-2-only device: "eui."=20
iSCSI/SAS combination device: "naa." since it is already using NAA
identifiers available for port names=20
SRP/iSCSI/SAS combination device: "naa." or "eui." since it already has
NAA and EUI-64s for port names=20

This would divorce the device name concept from the transport =
protocols.
Transport protocols could still require their devices have a device
name, but wouldn't comment on the format.

--=20
Rob Elliott, elliott at hp.com=20
Industry Standard Server Storage Advanced Technology=20
Hewlett-Packard=20



------_=_NextPart_001_01C27A2A.6A96E265
Content-Type: text/html;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">

SCSI device names The current rule in SAM-3 is that a = device may have one device name per transport protocol.  This = means, for example, that a target device with both SAS and iSCSI target = ports has two device names - the iSCSI name and the SAS device = name. Assuming 02-254 (WWNs for W-LUNs) = passes, these would be returned as two device identifiers in VPD = data: 
1. SAS device name 
association=3Dtarget device = (2h) 
protocol identifier=3DSAS (6h) 
identifier type=3DNAA (3h)  = 
identifier=3DIEEE Registered format = (NAA=3D5h), 8 bytes long 2. iSCSI device name 
association=3Dtarget device = (2h) 
protocol identifier=3DiSCSI = (5h) 
identifier type=3DiSCSI name-based = (7h)    (to be proposed in 02-419) 
identifier=3DUTF-8 format string, up = to 224 bytes long It would be simpler if there were only = one device name for a device. Since only iSCSI has defined device = names to date (SAS is just planning to include a device name now, and = FCP-3 might define one too), we have an opportunity to make all device = names follow the iSCSI name-based format and let each device have a = single device name regardless of protocol.  The iSCSI name format is a UTF-8 = (similar to ASCII) string that starts with a naming authority: 
;iqn.;  for an = iSCSI-defined reverse domain name string (e.g. = ;iqn.2001-04.com.acme:storage.disk2.sys1.xyz;) 
;eui.;  for a = hexadecimal representation of an EUI-64 identifier (e.g. = ;eui.02004567A425678D;) iSCSI could easily add an = ;naa.; type to carry a hexadecimal representation of an NAA = identifier (e.g. ;naa.52004567A425678D;), needed to carry the = format used by SAS and Fibre Channel port names. Then, a target device with target = ports of different protocols could use any string format it likes as = its sole device name. Likely choices: 
iSCSI-only device: ;iqn.; = (it may have no hardware names available) 
SAS-only device: = ;naa.; 
FC-only device: = ;naa.; 
SRP-only device: = ;eui.; 
SBP-2-only device: = ;eui.; 
iSCSI/SAS combination device: = ;naa.; since it is already using NAA identifiers available = for port names 
SRP/iSCSI/SAS combination device: = ;naa.; or ;eui.; since it already has NAA and = EUI-64s for port names This would divorce the device name = concept from the transport protocols. Transport protocols could still = require their devices have a device name, but wouldn't comment on the = format. -- 
Rob Elliott, elliott at hp.com 
Industry Standard Server Storage = Advanced Technology 
Hewlett-Packard 

------_=_NextPart_001_01C27A2A.6A96E265--




More information about the T10 mailing list