Re: Why REPORT LUN only for SCSI-2?

[Patrick Mansfield <patmans@us.ibm.com>]

On Wed, Jul 16, 2003 at 09:00:10AM +0200, Josef Möllers wrote:
> Patrick Mansfield wrote:

> So, can I cast my vote to drop it? Or at least change it to a check for
> SCSI_1.
> 
> The code does work with SCSI-2 devices (some disks) which don't support
> REPORT LUNs and IMHO devices which do support command code A0h for
> anything other than REPORT LUNs _are_ broken.

But some broken devices might hang when sent a REPORT LUN command, and
then we have to add a BFLAGS_NO_REPORT_LUN or some other hacks. 

We could change BLIST_LARGELUN to be BLIST_SCSI_3, and take that to mean
use REPORT LUN, and go up to the LLDD's max_lun (though I dislike adding
anything to the device_info table, especially when these devices should
report back as SCSI-3). Any multi-lun device that wants LUN > 8 better not
hang on a REPORT LUN.

> > Are the unconfigured LUNs showing up as if they were configured?
> 
> Yes

Are the PQ values of the extra drives coming back as 1?  If so the devices
will show up under sd but be offline. I can resend a patch for this, I got
no comments last time it went out.

You can easily tell if run with scsi scan logging, either boot with:

	scsi_mod.scsi_logging_level=0x00000180

Or before insmod of the adapter:

	echo scsi log scan 6  >/proc/scsi/scsi

> > Most disk/RAID arrays made in the last few years can configure whether
> > they report back as SCSI-2 or SCSI-3. It would be best if you could change
> > the device to report as SCSI-3.
> > 
> > Even some SCSI disk drives are capable of reporting back as SCSI-2 or
> > SCSI-3.
> 
> No, unfortunately we cannot change this. I've tried, but the vendors
> (these are OEM parts, it's not only the MYLEX thingies shown above)
> refused.
> I guess (I haven't dug into this deep enough, I'm not a standards
> person) is that the parts aren't 100% SCSI-3, connected to a
> FibreChannel HA. They are capable of addressing more than 8 LUNs.
> Adding them to the device_table doen't really work, because then we get
> 128 LUNs showing up and I have seen pretty large configurations with
> several RAID boxes connected so we run out of device numbers.

For linux 2.6 SCSI-3 (generally) means we will send a REPORT LUN, and we
will allow sequential scans past lun 8, and that would be fine in your
case.

You mean making the device BLIST_SPARSELUN in the scsi_static_device_list
or device_info gives you 128 LUNs?

-- Patrick Mansfield
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