Alternate Paths

[Steve Massey_1]

I currently have and VG on 1 H/W path.
I want to add a additional alternate H/W path for redundancy.
Has anyone done this or have advice to offer

Thanks

Steve

[Navied Yousuf]

Greetings,

You can use vgextend to create an alternate link. syntax is as follows.

#vgextend volume-group-name physical-volume-name

First you must find the alternate path for the physical volume already defined in your volume group via a primary path.
#vgextend /dev/vgxx /dev/dsk/cxtydz
where cxtydz refers to alternate path.
CAUTION: DON'T pvcreate the disk via alternate path, because you have already done via primary path.
NY

[CHRIS_ANORUO]

Hello,

You can do that before ISL prompt.

[Steve White_1]

It is no problem to connect 2 SCSI controllers to provide an alternate path. You have to be careful with the controller's address, if they are on one continuous bus you will have to change the SCSI id on the second controller.

I would want the second controller to have the SCSI id = 6

[Dave Wherry]

Do you have devices that are dual ported? You can't do alternate links with all disk devices. Typically you need some sort of array. You can't do it for internal disks or Jamaicas.
If you have a dual ported device and all the cables are connected, you can find the alternates using ioscan and then simply use vgextend to add them. They will automatically become alternates. Nothing special to do. Just check the vgextend man page.

[David Meidam]

All the responses are right on. Assuming that you are on a jamaica, FCxx, xp, etc. alternate links are fine. You could also specify them alternate path in a vgcreate. The first device file you specify is the primary and the second device file becomes the alternate.

[Carlos Fernandez Riera]

When we share to scsi cards between two boxes, Hp?s engenier uninstall internal resistors of both cards,and sets diferent SCSI ids to 7 and 6, because it is same bus.
you should install auto terminated cables too.