Mohan, it's been two days, so it doesn't look like anyone that would be an authority on this is going to answer.
I'm not an authority, but I've had similar problems in older versions of Red Hat and with a different SAN HBA and driver. I have no RHEL6 experience yet with this, but...
The questions I would ask are, how many paths do you have to the 256 LUNS? Do you only have 232 /dev/sdX devices showing, or is it up at the DM-Multipath layer that they're missing?
(My guess (without enough information to go on) is that your problem is not with DM-Multipath, but below that.)
If they're missing at the SCSI layer, 'lsscsi' will show that ('lsscsi | wc -l' to count the number of scsi devices plus your LUNS * paths).
See the following info at
http://support.bull.com/ols/product/...inst/PrKB11417
Quote:
LUN number supported
The maximum number of LUNs depends on a few factors:
the SCSI kernel module
the adapter module
If you run the command "modinfo scsi_mod" you will see the following output: (For current values, check out the files under /sys/module/scsi_mod/parameters.)
parm: max_luns: Last SCSI LUN (should be between 1 and 2^32-1) (int) This works out at 4,294,967,295, which is large.
parm: max_report_luns: REPORT LUNS maximum number of LUNS received (should be between 1 and 16384) (int) (See http://en.wikipedia.org/wiki/SCSI_Report_LUNs_Command for reference.) The maximum value the SCSI layer will allow when using REPORT LUNS is 16384.
It also depends on the driver being used, as the limit can also be set by the HBA driver, ie, most drivers such as qla2xxx and lpfc have module parameters that allow you to support large numbers of devices: (check the command "modinfo lpfc")
parm: lpcf_max_luns: Maximum allowed LUN (int)
# modinfo lpfc
These values can range from 8, for older parallel SCSI drivers, up to the maximum number of supported SCSI devices for Fibre Channel.
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'modinfo scsi_mod' doesn't seem to show too much; 'cat /sys/module/scsi_mod/parameters/max_luns' shows 512 and 'cat /sys/module/scsi_mod/parameters/max_report_luns' shows 511 on my RHEL6.1 and 5.6 systems. 'modinfo lpfc' may show you something.
I would look at the documentation for your Emulex LPe12002 HBA driver to see if there is a parameter there that you can specify if you are missing the low level SCSI devices (the /dev/sdX's).
Hope this helps.
