SCSI device names
gop at us.ibm.com
Wed Oct 23 08:02:56 PDT 2002
* From the T10 Reflector (t10 at t10.org), posted by:
* George Penokie <gop at us.ibm.com>
My first reaction was 'are you crazy'! My second reaction was 'we maybe
that would be a good idea'. But after thinking about it for awhile I don't
know why we would want to define a device name for SAS devices that is a
different format than the SAS address we already have which is already
unique. So we would end up with two different formats for WWN is SAS for no
real good reason. Also one of the formats would be ridiculously long.
Bye for now,
Dept 2C6 114-2 N212
E-Mail: gop at us.ibm.com
External: 507-253-5208 FAX: 507-253-2880
(Server Storage)" To: <t10 at t10.org>
<Elliott at hp.com> cc:
Sent by: Subject: SCSI device names
owner-t10 at t10.org
10/22/02 07:23 PM
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=target device (2h)
protocol identifier=SAS (6h)
identifier type=NAA (3h)
identifier=IEEE Registered format (NAA=5h), 8 bytes long
2. iSCSI device name
association=target device (2h)
protocol identifier=iSCSI (5h)
identifier type=iSCSI name-based (7h) (to be proposed in 02-419)
identifier=UTF-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.
"eui." for a hexadecimal representation of an EUI-64 identifier (e.g.
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.
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
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