The Effect of Device Replacement on Agile Device Files

Figure 6 shows FRU replacement with spoofing.
Figure 6: FRU Replacement (with target WWN spoofing)
Even though both the target and the LU are replaced, because the device is spoofing the old target
name (WWN), the target path does not change. However, because of the LUN-LU mapping change,
HP-UX detects a new LU behind the target and flags this as an authentication failure. In this case, you
must authenticate the use of new LU before accessing the LU as follows:
1131:/>scsimgr replace_wwid –D /dev/rtape/tape1 dsf
You must use the dsf keyword to avoid changing the device special file.
In addition, the SCSI stack also logs the following message to alert the system administrator:
Evpd inquiry page 83h/80h failed or the current page 83h/80h data do not match
the previous known page 83h/80h data on LUN id 0x0 probed beneath the target path
(class = tgtpath, instance = 3). The lun path is (class = lunpath, instance = 0).
Run 'scsimgr replace_wwid' command to validate the change.
If the device only spoofs the LU WWID and not the target port WWN, HP-UX detects this as a new
path to the LU. There is no change to the device file, but the path through the old target transitions to
the NO_HW state. You can clean the stale path using the rmsf command (rmsf –H lunpath).
If both the target and LU WWIDs are spoofed, there is no impact to the path or the device file
associated with the LU. Because the replacement is completely transparent to the host operating
system, applications can continue to use the existing device file after the FRU has been successfully
replaced.
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