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PV links

 
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Occasional Contributor

PV links

could someone confirm the below is the correct process to set up pathing and add a volume to a new volume group.

1. ioscan fnC disk
2. insf -H and add in new file to sdf I need to do this with all the links that show NO_HW so if the disk has 4 paths to the disk there will be 4 files
3. ioscan fnC disk
4. pvcreate -v do this on the primary path then on the 3 alternate paths.
5. vgcreate - v vg_myvolume /dev/dsk/cxxtxxdxx
5. if needed i can then change the time outs on the pv
6 pvchange -t 90 /dev/dsk/cxxtxxdxx
7 pvchange -p n /dev/dsk/cxxtxxdxx
I am new to HPUX so any advice with be greatfully received. As I understand it the above applies to V2 once you are on V3 you no longer have to doing the alternative path???
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Esteemed Contributor

Re: PV links

Hi,

> As I understand it the above applies to V2 once you are on V3 you no longer have to doing the alternative path???


Concept of PV links is completely deprecated on a 11.31 operating system or in terms of version the 11iv3 operating system. This is because multipathing is "native" to the operating system. However, traditionally HPUX used the concept of PV links and was also one of the aspects that relates to high availability when you talk in terms of "dual cabling" but again PV links had limitations, as load was transferred only accross one and not both cables but the "native" feature on 11.31 not only has all paths "active", algorithms are built in by default for the balancing of I/O load and the algorithms can also be set with the command scsimgr.

Characteristics of the PV are changed with the pvchange command which is a way of specifying the "link". If you are using v3 forget about a "PV link". Welcome to ITRC.

Regards
Ismail Azad

Read, read and read... Then read again until you read "between the lines".....
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Honored Contributor

Re: PV links

Looks good !! but you need to use vgextend vgname to enable all PV links visible to vg & can be displayed by vgdisplay -v.

Thanks
Manix
HP-UX been always lovable - Mani Kalra
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Occasional Contributor

Re: PV links

Could I just use
Pvcreate -v on the second path after I have done the primary?

Pvcreate -v \dev\dsk\c10t01d01 to set primary then

pvcreate -v to the alternate path

Thanks for your input it really helps a windows guy
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Acclaimed Contributor
Solution

Re: PV links

HI:

There is no need to do a 'pvcreate' on an alternate link. Alternate (or 'pvlink's) are simply different paths to the same physical disk.

Hence, initially, you could 'pvcreate' against all of the device files that point to a particular disk. This wouldn't harm anything but would be needless. *After* you 'vgcreate' a volume group, though, do not run 'pvcreate' against any paths that constitute the same physical device. A 'pvcreate' without the '-f' option will prevent this, though.

As for "primary" and "alternate" links, a 'primary' link is simply the first (of up to 8) paths to a device in '/etc/lvmtab'. A secondary or 'alternate' link can be promoted to a 'primary' one by a 'vgreduce' of the primary link followed by the re-addition of the old primary link with a 'vgextend'. In this way, a configuration of only a primary and one secondary link can be reconfigured to exchange the links.

Regards!

...JRF...
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Honored Contributor

Re: PV links

you don`t need to run "pvcreate " on the same physical device rather run vgextend vgname to add them.
HP-UX been always lovable - Mani Kalra