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Disk Issue

 
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Rkumar
Frequent Advisor

Disk Issue

Dear experts,

(Alternate links represent the same Physical volume.)
Please suggest me how to make sure that alternate links are indicating the same disks.

Please suggest on this

Rahul


9 REPLIES
Benoy Daniel
Trusted Contributor

Re: Disk Issue

is it connected to XP arrary?. Then use xpinfo -il and see the CU:LDev value. It will be same for primary and alternate link.
Bill Hassell
Honored Contributor
Solution

Re: Disk Issue

An alternate link is checked by LVM software when you extend a VG with a PV device file and the VG serial number matches. Every PV contains a unique serial number (created by pvcreate) and when added to a VG, contains the serial number for the VG. You can read this information with these commands:

First, set the PV filename:
PVFILE=/dev/rdsk/CTD

This shows the LVMREC on the disk.
dd if=$PVFILE bs=1k skip=8 count=1|xd -xc|head -10

This shows the PVID, the CPUID and the VGID.
xd -An -j8200 -N16 -tx $PVFILE

For the primary and alternate links, the numbers will be identical (they come from the same disk).


Bill Hassell, sysadmin
Kapil Jha
Honored Contributor

Re: Disk Issue

There are a couple of ways in addition to above

if you have powermt it would show you which disks are alternate, but then you don need to worry about adding alternate disk in VG.

in cXtXdX for alternate disk normally only cX changes so all disk with sam tXdX are one disk.

eg c1t0d0,c2t0d0,c3t0d0...would be same disk.

if you have huge number of disks then yeh it can be lil headache :)

BR,
Kapil+
I am in this small bowl, I wane see the real world......
lbseraph
Advisor

Re: Disk Issue

Additional method:

In HP-UX11iv3, can use below command to confirm the disks info.
#ioscan -m dsf
Rkumar
Frequent Advisor

Re: Disk Issue

Dear experts,

In my one box c1t0d0 is primary disk and c2t0d0 is mirror. as per Kapil's relpy c2t0d0 must be link to c1t0d0.

Please suggets on this.


Rahul
Chandrahasa s
Valued Contributor

Re: Disk Issue

If your os is v3 you can use ioscan -m dsf

this will show persistent and legacy path where you can easily identify alternate path

or if storage is hp

use xpinfo
if emc use powermt display dev=all

Chandra

Kapil Jha
Honored Contributor

Re: Disk Issue

can you please post

strings /etc/lvmtab
and do you have powermt display.
which SAN is this, or local disk.


BR,
Kapil+
I am in this small bowl, I wane see the real world......
Kapil Jha
Honored Contributor

Re: Disk Issue

have u tried the command as suggested by Bill

xd -An -j8200 -N16 -tx /dev/rdsk/cxtcdx

BR,
Kapil+
I am in this small bowl, I wane see the real world......
chris huys_4
Honored Contributor

Re: Disk Issue

Hi Rahul,

Draw youre own, IO design of the system and from there draw conclusions, if any disks/luns have more then 1 path.

NOTE: Almost allways, alternate paths/links to a disk/lun will have the same (cX/V/W)tydz device file name, but not necessarily all (cX/V/W)tydz device files will point to the same disk/lun. Which is probably the case in youre situation, c1t0d0 is not an alternate path to c2t0d0 but points to a seperate disk.

For internal disks, crosscheck the ioscan -fn output (for pre HP-UX 11iv3), ioscan -fn/ioscan -fnN/ioscan -fne/ioscan -m dsf (for HP-UX 11iv3), with the IO design that can be found in the hardware guide of the system.

F.e. for a rx7640, the hardware guide can be found via docs.hp.com,

"
HP Integrity rx7640 and HP 9000 rp7440
Servers
User Service Guide
"
http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c01883971/c01883971.pdf

On page 28 the internal disks IOpaths can be found.

with 4 internal disks inserted, 4 paths are listed.

Drive 1-1 - 1/0/0/3/0.6.0
Drive 1-2 - 1/0/1/1/0/4/1.6.0
Drive 0-2 - 0/0/1/1/0/4/1.5.0
Drive 0-1 - 0/0/0/3/0.6.0

And compare this info with the output of ioscan -fn.

titan:/root:model
ia64 hp server rx7640

titan:/root:uname -a
HP-UX titan B.11.31 U ia64 2146251420 unlimited-user license

titan:/root:ioscan -fn|more
[..]
ext_bus 0 1/0/0/3/0 mpt CLAIMED INTERFACE SCSI Ultra32
0
/dev/mpt0
disk 1 1/0/0/3/0.6.0 sdisk CLAIMED DEVICE HP 73.4GST37
3455LC
/dev/dsk/c0t6d0 /dev/rdsk/c0t6d0
[..]
ext_bus 1 1/0/0/3/1 mpt CLAIMED INTERFACE SCSI Ultra32
0
/dev/mpt1
target 1 1/0/0/3/1.2 tgt CLAIMED DEVICE
disk 0 1/0/0/3/1.2.0 sdisk CLAIMED DEVICE Optiarc DVD
RW AD-5170A
/dev/dsk/c1t2d0 /dev/rdsk/c1t2d0

The above host has only access to 1 internal disk, which has only 1 path to the internal disk.

Greetz,
Chris