SCSI device names

Elliott, Robert (Server Storage) Elliott at hp.com
Wed Oct 23 08:23:36 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
A SAS-only device would still base its device name off an NAA
identifier.  It would just be expressed as "naa.5WWWXXXXYYYYZZZZ" rather
than as an 8 byte binary value.

We can mandate that those identifiers still share the NAA namespace (as
"eui." would share the EUI-64 namespace).

What it helps solve is a device that has both ports using different
transport protocols, where two or more device names would be needed
under current rules.  This is a big complication for software. Since the
string format is capable of expressing all 3 in use today - "iqn."
"eui." and "naa." - it seems like the best candidate.

This problem also affects the logical unit name (association 0h).  A
native SAS or FC device will want to use an NAA format; an InfiniBand
SRP device will want to use an EUI-64 format; an iSCSI device will want
to use an "iqn." based format.  If the target device has target ports
with all those protocols, how does it choose?  I think the only answer
is "any of them it wants."

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



> -----Original Message-----
> From: George Penokie [mailto:gop at us.ibm.com] 
> Sent: Wednesday, October 23, 2002 10:03 AM
> To: Elliott, Robert (Server Storage)
> Cc: t10
> Subject: Re: SCSI device names
> 
> 
> 
> 
> 
> 
> Rob,
> 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,
> George Penokie
> 
> Dept 2C6  114-2 N212
> E-Mail:    gop at us.ibm.com
> Internal:  553-5208
> External: 507-253-5208   FAX: 507-253-2880
> 
> 
> 
> 
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>                       "Elliott, Robert                        
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>                       (Server Storage)"        To:       
> <t10 at t10.org>                                                 
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>                       <Elliott at hp.com>         cc:            
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>                       Sent by:                 Subject:  SCSI 
> device names                                                  
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>                       owner-t10 at t10.org                       
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>                       10/22/02 07:23 PM                       
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> 
> 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.
> "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
> 
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