adding alternate links

[ROSS HANSON]

I have VG05 and VG06 already up and running. Both volume groups have an alternate link in case a SAN Controller goes down.
On a storage array I created two new luns 300GB in size each I did a pvcreate of each lun then added one to VG05 and one to VG06 using vgextend.

vgextend /dev/vg05 /dev/dsk/cxtxdx <-- one lun
vgextend /dev/vg06 /dev/dsk/cytydy <-- second

Can I now add an alternate link to each side in case a controller goes out?

[Patrick Wallek]

Yes. Just use vgextend again to add the alternate path for each LUN.

[Sunny123_1]

Hi

Your steps are correct go ahead and add alternet link also.

Regards
Sunny

[ROSS HANSON]

OK,
I have done it now my vgextend command looks like this:

vgextend /dev/vg05 /dev/dsk/cytydy

but I receive an error message back saying:

vgextend: The physical volume /dev/dsk/cytydy is already recorded in the /etc/lvmtab file

[Ron Irving]

Ross,

Please post the output of
# strings /etc/lvmtab

thx

[Patrick Wallek]

You tried to add the path to your 2nd lun as the alternate path for the first lun. That will NOT work.

You need to go through 'ioscan -kfnC disk' and find the actual alternate paths for the 2 luns.

[ROSS HANSON]

# strings lvmtab
/dev/vg00
E5 C
/dev/dsk/c2t0d0s2
/dev/dsk/c2t1d0s2
/dev/vg05
/dev/dsk/c15t0d1
/dev/dsk/c19t0d1
/dev/dsk/c15t0d5
/dev/vg06
/dev/dsk/c15t0d2
/dev/dsk/c19t0d2
/dev/dsk/c15t0d4

The first two paths seen on vg05 and vg06 are the originals. The /dev/dsk/c15t0d5 is the lun/disk I added this morning. The same goes for vg06, the last entry is what I entered this morning to the vg

[Patrick Wallek]

*****
/dev/vg05
/dev/dsk/c15t0d1
/dev/dsk/c19t0d1
/dev/dsk/c15t0d5
/dev/vg06
/dev/dsk/c15t0d2
/dev/dsk/c19t0d2
/dev/dsk/c15t0d4
*****

It appears that your alternate paths are the c19 disks.

If that is the case, to add your alternate paths for your new disks you would do:

# vgextend vg05 /dev/dsk/c19t0d5
# vgextend vg06 /dev/dsk/c19t0d4

[ROSS HANSON]

OK,

Now my /etc/lvmtab looks like this:

# strings /etc/lvmtab
/dev/vg00
E5 C
/dev/dsk/c2t0d0s2
/dev/dsk/c2t1d0s2
/dev/vg05
/dev/dsk/c15t0d1
/dev/dsk/c19t0d1
/dev/dsk/c15t0d5
/dev/dsk/c19t0d5
/dev/vg06
/dev/dsk/c15t0d2
/dev/dsk/c19t0d2
/dev/dsk/c15t0d4
/dev/dsk/c19t0d4

One last question though... Now when I do a vgdisplay on, for example /dev/vg06 I receive this:

--- Physical volumes ---
PV Name /dev/dsk/c15t0d2
PV Name /dev/dsk/c19t0d2 Alternate Link
PV Status available
Total PE 25596
Free PE 36
Autoswitch On
Proactive Polling On

PV Name /dev/dsk/c15t0d4
PV Name /dev/dsk/c19t0d4 Alternate Link
PV Status available
Total PE 38394
Free PE 38394
Autoswitch On
Proactive Polling On

should not both sides be reporting the same Total PE and Free PE ?

[Patrick Wallek · Accepted solution]

************
One last question though... Now when I do a vgdisplay on, for example /dev/vg06 I receive this:

--- Physical volumes ---
PV Name /dev/dsk/c15t0d2
PV Name /dev/dsk/c19t0d2 Alternate Link
PV Status available
Total PE 25596
Free PE 36
Autoswitch On
Proactive Polling On

PV Name /dev/dsk/c15t0d4
PV Name /dev/dsk/c19t0d4 Alternate Link
PV Status available
Total PE 38394
Free PE 38394
Autoswitch On
Proactive Polling On
*******************

>>should not both sides be reporting the same Total PE and Free PE ?

No. For device c15t0d2/c19t0d2, you have 25,596 PEs total on the device. All but 36 of those have been used by an LV.

On c15t0d4/c19t0d4 you have a 38,394 PE's total on the device. NONE of them have been assigned to / used by an LV yet.