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Finding alternate paths to disk

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Rich Owens_1
Occasional Visitor

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
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
Occasional Visitor

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
Occasional Visitor

Re: Finding alternate paths to disk

Thanks for the replies. Good luck with the AIX box Victor.
Jesse Reyes
Occasional Visitor

Re: Finding alternate paths to disk

Rich,

We are also in the process of connecting a Hitachi Storage subsystem to a N4000 Server thru Fiber. What type of HBA's are you using?
Dave Wherry
Esteemed Contributor

Re: Finding alternate paths to disk

Rich,
Did you get the array from Hitachi or is it a XP256/512?
If it is a XP you can get a utility called xpinfo. I would imagine that Hitachi would have something similar.
Anyway, scripting is not my strong suit, but, you could do a script that essentially follows this logic.
Do "xpinfo -il"
This will give you a listing of the LUNs on your host. It is ordered by LDev number. It also has the device file for each port that the LDev is assigned to. For each LDev do a pvdisplay on the device file. You will see if it is in a volume group. If not it might be an alternate link that is not added to a volume group. If all device files for an LDev are not in a volume group, it is available. From this you could produce a list of available disks.
I'm not thinking it all the way through, I have to get back to something else right now. I don't think it would be that hard. Just playing with it here I've found some alternate links I do not have setup. I will be working with this more in the next few days.
M Batteux
Occasional Visitor

Re: Finding alternate paths to disk

Hi Rich,

the only way i've found to get informations about alternate path : by SAM/Disks and File Systems
... no warranty but it works !

best regards

Alain Guillaume
Mark van Hassel
Respected Contributor

Re: Finding alternate paths to disk

Hi Rich,

You don't have to worry about someone else trying to destroy your vg with pvcreate: as long as the "-f" option is not used !
pvcreate will return an error indicating that the pv is already in use. pvdisplay will then indicate that it is configured in a vg..
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