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Re: Finding alternate paths to disk

 
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Rich Owens_1
New Member

Finding alternate paths to disk

We have an HITACHI array attached to our N4000 via 2 fiber channels. Without adding disks to a volume group and running vgdisplay is there any way to identify the alternate paths to a disk if you did not know how the disks are connected?
13 REPLIES 13
Brian M. Fisher
Honored Contributor

Re: Finding alternate paths to disk

Run ioscan -fnC disk
This will list the I/O paths to the disks

Brian
<*(((>< er
Perception IS Reality
Maarten van Maanen
Regular Advisor

Re: Finding alternate paths to disk

Rich,

You could running ioscan -fnC disk or you can look at your /etc/lvmtab file, which will also give you the Volume Group to disk configuration.
Rick Garland
Honored Contributor

Re: Finding alternate paths to disk

If you are running perl 5, here is a script I use frequently. This script will detail the alternates, mirrors, stripes, etc...
Rich Owens_1
New Member

Re: Finding alternate paths to disk

Yes, I know you can run ioscan -fnC. My questions was "without adding the devices to a volume group or knowing the HW setup". I do not want to have to add all of the unused disks to a volume group in order for someone else to run vgdisplay to see that there are alternate paths. Here is some of the output from my ioscan. I know they are alternate paths but how would someone else know if they didn't know the HW was connected with dual controllers? They would think they had 4 drives when they actually only have one in this case. I'll sleep on it and the answer will probably come to me tomorrow.
disk 27 0/4/0/0.16.2.255.0.0.0 sdisk CLAIMED DEVICE HITACHI DF400F
/dev/dsk/c11t0d0 /dev/rdsk/c11t0d0
disk 33 0/4/0/0.16.3.255.0.0.0 sdisk CLAIMED DEVICE HITACHI DF400F
/dev/dsk/c12t0d0 /dev/rdsk/c12t0d0
disk 39 1/10/0/0.16.2.255.0.0.0 sdisk CLAIMED DEVICE HITACHI DF400F
/dev/dsk/c13t0d0 /dev/rdsk/c13t0d0
disk 45 1/10/0/0.16.3.255.0.0.0 sdisk CLAIMED DEVICE HITACHI DF400F
/dev/dsk/c14t0d0 /dev/rdsk/c14t0d0
Anthony Goonetilleke
Esteemed Contributor

Re: Finding alternate paths to disk

Yes I know what you mean and it can be frustrating especially if you have more than one admin. If the disks and the alt. paths are already in a volume group you could write a small script to grep all the paths and format it showing alternate and primary paths.

I also found this DOc when I was looking for a similar thing it has some good pointers..
Document Id UNX1030197
Minimum effort maximum output!
Andreas Voss
Honored Contributor

Re: Finding alternate paths to disk

Hi,

you could also use my shell scipt for finding alternate links within LVM.

Regards

Andrew
Victor BERRIDGE
Honored Contributor

Re: Finding alternate paths to disk

Hi,
I also have diff. HDS cabs, with not all disks assigned to vgs, and never was bothered by this point of view, because the alternate path were defined when you assigned your LUNs to the different controllers...
And of course I keep a paper copy of the HDS config, else you can use HDS sommet...
Now to see, just use pvdisplay:
# ioscan -funC disk
Class I H/W Path Driver S/W State H/W Type Description
======================================================================
disk 2 8/12.0.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c0t0d0 /dev/rdsk/c0t0d0
disk 3 8/12.1.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c0t1d0 /dev/rdsk/c0t1d0
disk 4 8/12.2.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c0t2d0 /dev/rdsk/c0t2d0
disk 5 8/12.3.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c0t3d0 /dev/rdsk/c0t3d0
disk 6 8/12.4.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c0t4d0 /dev/rdsk/c0t4d0
disk 7 10/0.0.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c1t0d0 /dev/rdsk/c1t0d0
disk 8 10/0.1.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c1t1d0 /dev/rdsk/c1t1d0
disk 9 10/0.2.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c1t2d0 /dev/rdsk/c1t2d0
disk 10 10/0.3.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c1t3d0 /dev/rdsk/c1t3d0
disk 11 10/0.4.0 sdisk CLAIMED DEVICE HITACHI DF400
/dev/dsk/c1t4d0 /dev/rdsk/c1t4d0
disk 0 10/0.6.0 sdisk CLAIMED DEVICE SEAGATE ST39173WC
/dev/dsk/c1t6d0 /dev/rdsk/c1t6d0
disk 1 10/12/5.2.0 sdisk CLAIMED DEVICE TOSHIBA CD-ROM XM-5701TA
/dev/dsk/c2t2d0 /dev/rdsk/c2t2d0
draco # pvdisplay /dev/dsk/c1t2d0
--- Physical volumes ---
PV Name /dev/dsk/c1t2d0
PV Name /dev/dsk/c0t2d0 Alternate Link
VG Name /dev/r5vg01
PV Status available
Allocatable yes
VGDA 2
Cur LV 3
PE Size (Mbytes) 4
Total PE 2842
Free PE 1580
Allocated PE 1262
Stale PE 0
IO Timeout (Seconds) default
Victor BERRIDGE
Honored Contributor
Solution

Re: Finding alternate paths to disk

Hi Rich
I just read your reply again and what you want to know is: Can someone else add a disk he believes not used because he is seeing an alternate link.
When I tried that some time ago, I remembered the system saying the disk is a alternate link thus not allowing you to do so, but this is true with HP-UX im fighting now with an AIX to do the same but with no success...
I suppose I tried also with a disk not beeing used yet, this is another case but I dont remember what happened and I have none available to try (I used to do my test on a DF350) I suppose the system would accept to extend or create a new vg with this disk but will invert the alternate path, I never had trouble with HDS arrays...
Rich Owens_1
New Member

Re: Finding alternate paths to disk

Thanks for the replies. Good luck with the AIX box Victor.