Alternate path on 12H

[Greg Stark_1]

We have an L2000 with a 12H with 2 controllers. After RAID and hot spare, we had about 50 gig usable left. We created 2, 25 gig luns and created a vg out of each (vg02 and vg03). We also setup primary and alternate paths to the luns.

We recently noticed some performance problems and found that both luns were using the same primary and alternate paths.

Can we change the primary path of one of the luns to the alternate path on the fly? Also, does this overall config seem sensible given our hardware (except that we left no free space for RAID 0/1).

Thanks again,
Greg

[Victor BERRIDGE · Accepted solution]

Hi,
e.g:
hooke1-> vgdisplay -v r5vg05|grep dsk
PV Name /dev/dsk/c6t0d3
PV Name /dev/dsk/c7t0d3 Alternate Link


hooke1-> vgreduce r5vg05 /dev/dsk/c6t0d3
Device file path "/dev/dsk/c6t0d3" is an primary link.
Removing primary link and switching to an alternate link.
Volume group "r5vg05" has been successfully reduced.
Volume Group configuration for /dev/r5vg05 has been saved in /etc/lvmconf/r5vg05.conf
hooke1-> vgdisplay -v r5vg05
--- Volume groups ---
VG Name /dev/r5vg05
VG Write Access read/write
VG Status available
Max LV 255
Cur LV 1
Open LV 1
Max PV 16
Cur PV 1
Act PV 1
Max PE per PV 10420
VGDA 2
PE Size (Mbytes) 4
Total PE 10418
Alloc PE 10000
Free PE 418
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0

--- Logical volumes ---
LV Name /dev/r5vg05/lvol1
LV Status available/syncd
LV Size (Mbytes) 40000
Current LE 10000
Allocated PE 10000
Used PV 1


--- Physical volumes ---
PV Name /dev/dsk/c7t0d3
PV Status available
Total PE 10418
Free PE 418
Autoswitch On


hooke1-> vgextend r5vg05 /dev/dsk/c6t0d3
Volume group "r5vg05" has been successfully extended.
Volume Group configuration for /dev/r5vg05 has been saved in /etc/lvmconf/r5vg05.conf
hooke1-> vgdisplay -v r5vg05
--- Volume groups ---
VG Name /dev/r5vg05
VG Write Access read/write
VG Status available
Max LV 255
Cur LV 1
Open LV 1
Max PV 16
Cur PV 1
Act PV 1
Max PE per PV 10420
VGDA 2
PE Size (Mbytes) 4
Total PE 10418
Alloc PE 10000
Free PE 418
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0

--- Logical volumes ---
LV Name /dev/r5vg05/lvol1
LV Status available/syncd
LV Size (Mbytes) 40000
Current LE 10000
Allocated PE 10000
Used PV 1


--- Physical volumes ---
PV Name /dev/dsk/c7t0d3
PV Name /dev/dsk/c6t0d3 Alternate Link
PV Status available
Total PE 10418
Free PE 418
Autoswitch On

Answer is yes, I done it (I didnt have the choice...)

All the best

Victor

[A. Clay Stephenson]

Hi Greg:

You're really not going to able to do this on the fly. The best bet is to vgexport using the -m option to create a mapfile and then do a vgimport swapping the paths on the 2nd LUN.

You definitely want to do this or your Y controller is just sitting there doing nothing.

[Steven Gillard_2]

Try:

pvchange -s

See the pvchange man page for more information.

Regards,
Steve

[nancy rippey]

You can use pvchange to change from primary to alternate
pvchange -s /dev/dsk/c#t#d#

Hope this helps.

nancy

[Christopher McCray_1]

Or, if you want to take another approach, use sam:

Disks and File Systems --> Disk Devices
Highlight the LUN you want and:

Actions --> Change Primary LVM Path

This will swap the Alternate to Primary

Hope this helps.

Chris

[Sridhar Bhaskarla]

You can make PV1 (altPV1) in vg02 on one path and altPV2 (PV2) in vg03 on another path on the fly. You can use pvchange to accomplish this but it will not last once the system is rebooted.

#pvchange -s PV1
#pvchange -s altPV2

To make it permanent, you don't need to touch vg02 as we want to retain PV1 on the primary path. Only on vg03, do the following

#vgreduce vg03 PV2 (note the primary path here)
#vgextend vg03 PV2

This will change the order that appears in /etc/lvmtab and hence the primary and alternate links.

-Sri