Alternate links for disk physical volumes

[Stuart Powell]

I have created a physical volume on a disk array that has two fibe channel interfaces. I used the command pvcreate /dev/rdsk/c4t0d6. I want to set up an alternate link at /dev/rdsk/c8t0d6. How do I do that?

Stuart

[Sanjay_6 · Accepted solution]

Hi Stuart,

You specify the alternate link when you create the VG. Since this is an autoraid, proceed like this,

pvcreate -f /dev/rdsk/c4t0d6
mkdir /dev/vg_name
mknod /dev/vg_name/group c 64 0x0n0000
(n=1,2,3,....and is unique, to find a unique no for n do "ll /dev/*/group)
vgcreate /dev/vg_name /dev/dsk/c4t0d6
vgextedn /dev/vg_name /dev/dsk/c8t0d6

Now do a "vgdisplay -v /dev/vg_name" and it will show the alternate link over there for the PV mentioned above.

Hope this helps.

Regds

[Sanjay_6]

Hi Stuart,

Here is a link from ITRC on the question you have asked,

http://us-support.external.hp.com/cki/bin/doc.pl/sid=1345381f01e701a649/screen=ckiDisplayDocument?docId=200000024626185

Here is a link from hp docs site

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-90742/B2355-90742_top.html&con=/hpux/onlinedocs/B2355-90742/00/00/48-con.html&toc=/hpux/onlinedocs/B2355-90742/00/00/48-toc.html&searchterms=vgcreate%20alternate%20link&queryid=20011116-134752

Look for "Tasks That You Can Perform Only with HP-UX Commands " --> "Setting Up Alternate Links to a Physical Volume"

Hope this helps.

Regds

[Darrell Allen]

Hi Stuart,

As you see from Sanjay's answer, the missing piece was the vgextend. Simply extending the VG with the second device path will indeed add it as an alternate link if it truly is the same disk / lun. If it doesn't show as an alternate link then it is not the same disk.

Darrell

[Craig Rants]

Here is what I do for my Autoraid with two channels.

# cd /dev
# mkdir vg0# (where # is the number of the volume group such as vg03)
# cd vg0#
# mknod group c 64 0x0#0000 ( # must be the same as the volume group number)
# pvcreate /dev/rdsk/c0t1d0 (do this for all 4 disks that are being added to the volume group)
# vgcreate /dev/vg0# /dev/dsk/c1t0d0 /dev/dsk/c2t1d0 /dev/dsk/c2t1d1
/dev/dsk/c1t0d1 (you must follow this format when adding disks into the volume group)
# vgdisplay ???v vg0# ( see if the volume group was created successfully, make sure controller cards alternate. It should look like the example below)
--- Physical volumes ---
PV Name /dev/dsk/c1t0d0
PV Name /dev/dsk/c0t1d0 Alternate Link
PV Status available
Total PE 4499
Free PE 1311
Autoswitch On

PV Name /dev/dsk/c0t1d1
PV Name /dev/dsk/c1t0d1 Alternate Link
PV Status available
Total PE 4499
Free PE 1311
Autoswitch On

if not correct
# vgreduce vg0# /dev/dsk/c#t#d#
# vgextend vg0# /dev/dsk/c#t#d#
then continue
if correct next step is to make the required mount points for a striped logical volume on autoRAID
# lvcreate ???l ???SIZE??? ???i 2 ???I 64 ???s y (???n lvol#) /dev/vg0# (repeat this for all logical volumes needed ??? The SIZE represents lvol size, the ???l is for extents, ???L for Mbytes default Physical Extent size is 4MB) ( the format above for stripping is lower case -i 2 upper case -i 64, Word distorts the true representation of the letters) don???t use the ???n option in most cases and pay attention to make sure that the you see what lvol it has assigned.
# newfs ???F vxfs /dev/vg0#/rlvol# (repeat this for all rvol???s needed)
# cd /etc
# vi fstab (Add new volume group with files as needed create needed directories)
ie.. /dev/vg0#/lvol# /opt/oracle vxfs delaylog 0 2
mount ???a (tests fstab entries while it mounts new lvol???s)
bdf (to show that they are mounted)


Good Luck,
C