SPC Report LUNs command

Steve Sicola...Array Controller Engineering 522-2268 sicola at Peaks.enet.dec.com
Thu Dec 12 12:45:11 PST 1996


* From the SCSI Reflector (scsi at symbios.com), posted by:
* "Steve Sicola...Array Controller Engineering 522-2268" <sicola at peaks.ENET.dec.com>
*
Array Controller Devices are the mother of LUN boxes. They will have to export
all the virtual-ness of a volume-set by way of association with a LUN address.

For future reference there has been a lot of work in un-associating a LUN
with the volume set for array controllers and allowing assignment of the 
association...

so to say that array controllers don't have LUN devices is an understatement...

Steve

From:	DECPA::"ron at core.rose.hp.com" "Ron Gould" 12-DEC-1996 10:38:32.43
To:	scsi at symbios.com
CC:	
Subj:	Re: SPC - Report Luns command

* From the SCSI Reflector (scsi at symbios.com), posted by:
* Ron Gould <ron at core.rose.hp.com>
*
>* From the SCSI Reflector (scsi at symbios.com), posted by:
>* ROWEBER at acm.org
>*
     .
     .
     .
>
>>From the Inquiry command, the application client can determine the device 
>type of the SCSI device at that bus ID.
>
>Device type is critical because:
>
>   - All device types except array devices have only "LUN devices"
>     (such devices do not have "peripheral devices" or "volume set devices")

Peripheral device addressing (addressing method 00b) is what is used for 
non-array controller devices.

>
>   - Array type devices have both "peripheral devices" and "volume set 
>     devices", but array devices do not have "LUN devices".  Finally,
>     "peripheral devices" can be differentiated from "volume set devices"
>     by inspecting their logical unit numbers in accordance with the
>     rules described in SCC (SCSI-3 Controller Commands).

Array controller devices not having "LUN devices" (I assume that the 
logical unit addressing method is what is being referred to) is news
to me, especially since the logical unit addressing method is defined 
by SCC (I'm looking at rev. 6).  Where is it specified that array
controller devices do not have "LUN devices".

>
>It also is important to note that SCC defines commands for accessing informa-
>tion about all logical unit devices defined within a storage array.  The SCC
>commands provide the control over what information is returned that Larry Chen
>requested in the original mail.
>
>Although it may not be immediately obvious, the features requested by Larry 
>Chen are already available in SCSI.  In most cases, only one type of LUN is
>reported by the Report Luns command.  In the only exception to that rule,
>commands other than Report Luns provide the requested selection capability.
>Therefore, no changes are required.

The only exception I know of is that array controller devices may report
all three types of LUNs (logical unit, peripheral device, and volume set).
An array controller device may report all of these in a single REPORT LUNS
command.  It is unclear to me what "commands other than Report Luns provide 
the requested selection capability".

>
>Thanks.
>
>Ralph...
>*
>* For SCSI Reflector information, send a message with
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>

Ron Gould
ron at core.rose.hp.com
*
* For SCSI Reflector information, send a message with
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% Subject: Re: SPC - Report Luns command
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