scsimgr.1m (2010 09)

s
scsimgr(1M) scsimgr(1M)
To prevent accidental data corruption, the SCSI stack implements an authentication
mechanism based on the LUN WorldWide Identifier (WWID). When a LUN with a
different WWID is discovered through a previously discovered LUN path, further access
to the device through that LUN path is prevented. The LUN path is put in "Authentica-
tion Failure" state. Then, HP-UX logs a message in
syslog which informs the user that
the
replace_wwid operation needs to be performed.
If the user has intentionally replaced the LUN, the
scsimgr replace_wwid com-
mand must be run to authorize the re-use of that LUN path for a different LUN.
In some situations, a replacement of a target controller may cause LUN paths of
corresponding target paths to be put in authentication failure state. To validate the
replacement and re-authorize all the affected paths,
scsimgr replace_wwid can be
used with the target path identifier.
If the LUN itself has been replaced and all its previous LUN paths are now connected to
the replaced LUN,
scsimgr replace_wwid can be used with the LUN identifier to
allow replacement of all LUN paths associated with that LUN.
If the keyword
dsf is specified, the DSF of the replaced LUN is re-assigned to the new
LUN. This allows applications such as volume groups or file systems to continue to use
the same DSF to access the replacing LUN.
If a LUN has more than one persistent DSF, each of its persistent DSFs would be reas-
signed. To achieve this reassignment, scsimgr invokes the io_redirect_dsf command.
Note that this command may require the number of persistent DSFs of the replaced LUN
and the new LUN to be equal. See io_redirect_dsf(1M).
This authentication mechanism replaced the one implemented by Fibre Channel Tachyon
TL, Tachyon TL2 and FCD drivers on releases prior to HP-UX 11i Version 3. The
scsimgr replace_wwid command combined with the scsimgr
replace_leg_dsf command replaces the
fcmsutil replace_dsk command. See
the explanation of the
scsimgr replace_leg_dsf
command and the fcmsutil (1M)
manpage.
Usage:
scsimgr [-f] replace_wwid identifier [dsf]
Note: identifier identifies a LUN, LUN path, or a target path. In case of LUN replace-
ment (that is, the identifier is a LUN), the keyword
dsf directs replace_wwid to also
assign the device file name of the replaced LUN to the new LUN. If the identifier is a
LUN path, or target path, dsf is just ignored.
WARNING: for disk arrays, if the WWID of the LUN representing the array controller
(LUN with identifier 0) changes, all lunpaths of that target port will go to
NO_HW state on
a subsequent ioscan, resulting in a loss of access to the array controller. This will cause
the host OS to no longer probe and discover the LUN inventory behind that array con-
troller, leading to all LUNs behind that target port going to
NO_HW state on a subsequent
ioscan. To re-enable probing and discovery of the LUN inventory behind the target port,
the user should run the scsimgr replace_wwid command on the LUN representing
the array controller.
save_attr Saves values, persistently, of global attributes or attributes of a single SCSI object. If the
keyword default is specified, or the argument is of the form: "-a attr =default",
then the default value is restored persistently across system reboots.
If the keyword default is not mentioned and the argument is of the form:
"
-a attr =value", then the current value is replaced with the specified value, and it is
saved in a persistent store.
Attribute values saved in a persistent store are maintained across reboots.
Only values of attributes that are settable or read-write values can be saved. To view the
settable values, use
get_attr command with the keyword settable. In case of the
value being saved is a string including a space, it should be put within double quotes
("...").
If no identifier or keyword for a group of SCSI objects is specified, attributes specified
should be global generic attributes.
12 Hewlett-Packard Company − 12 − HP-UX 11i Version 3: September 2010