The most visible change to the mass storage stack in
HP-UX 11i v3 is the addition of agile addressing, also known as persistent
LUN binding . With the introduction
of agile addressing, there is only a
single DSF for each unique LUN in the
server, no matter how many lunpaths the LUN has or if any of those lunpaths
change.
Earlier releases HP-UX, the legacy addressing is used
and each LUN will be having a separate device file for the Fibre Channel paths
available on that server.
With the agile addressing,
Before configuring Volume Groups on a new HP-UX 11.31
server, the SPC -2 (SCSI Primary Commands -2) flag needs to be enabled. This
flag is enabling at the port level / FA level from the storage side. Unix
engineer need to engage the Storage team for enabling this flag. If the Flag is not configured properly for a
server, the performance of other 11.31 servers
which are connected to the same FA
will get degraded even though those servers have the SPC flag enabled. After
enabling the flag, the server need to be restarted .
The SPC settings can be verified with scsimgr command. Please
find the o/p from where a server where SPC flag is not enabled.
hp461#
scsimgr get_info -D /dev/rdisk/disk3 |grep -i spc
SPC
protocol revision
= 2
If the SPC flag is enabled the o/p will be,
hp461#
scsimgr get_info -D /dev/rdisk/disk3 |grep -i spc
SPC
protocol revision
= 4
If the SPC flag
is not enabled for a server, there will be more than one device files for for a
LUN and will be same as the number of FC paths in the server. Suppose a server
is having 2 FC cards & SPC flag is not enabled, the disk details will be as
follows.
hp470#
ioscan -m dsf /dev/rdisk/disk12
Persistent
DSF Legacy DSF(s)
========================================
/dev/rdisk/disk12 /dev/rdsk/c5t14d7
And if we try to create / import a Volume Group on the
server, the below errors will be coming.
#vgimport -v -s -N -m
/tmp/hp404_vg125.map /dev/vg125
Beginning the import process on Volume Group "vg125". Verification of unique LVM disk id on each disk in the volume group /dev/vg125 failed. Following are the sets of disks having identical LVM disk id /dev/disk/disk510 /dev/disk/disk740
Root-cause
:
|
In an HP-UX server, there will be a lunpath for all the active FC cards configured for the disk.
In earlier releases
of HP-UX , there will be a device file
for each FC path to a LUN. Normally the server treats one path as primary path
and the others as the alternate paths to the LUN. In 11.31, if the flag is not
enabled , the server will treat each
path as a separate disk. Because of this if we try to use the disk for creating
the VG, we are getting the error “Following are the
sets of disks having identical LVM disk id “.
Once
the SPC flag is enabled, there will be only DSF for a LUN irrespective of the
number of FC paths configured on the server.
The
o/p of the LUN status from a server
where the flag is enabled will be as follows,
hp470#
ioscan -m dsf /dev/rdisk/disk12
Persistent
DSF Legacy DSF(s)
========================================
/dev/rdisk/disk12 /dev/rdsk/c5t14d7
/dev/rdsk/c4t14d7
Note: This server is having 2 FC
paths configured for disks.
1 Comments
TEMPORARY WORKAROUND to force the vgimport to configure the volume group anyway: Use the command "rmsf" on all the "identical disk ID" legacy device files that were reported by the failing vgimport command. Then try again with vgimport and it will work. However, the volume group will now run without "Alternate Links" on it's LUNs !
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