topic Re: Exporting and importing volumes groupe to an other serveur in Operating System - HP-UX

Exporting and importing volumes groupe to an other serveur

CSP_ALGERIA — Wed, 26 Mar 2003 09:55:33 GMT

hello ,

we have two serveurs Hp9000 (rp8400) running under hpux 11i.
we use the first one as a principal serveur with diferent volumes groupes created using servral LUNs in a VA 7410 ( about 64 Lun ).

we wante to use the second serveur as a backup serveur if the first one fail ( with out using MC service guard ).

when we do an ioscan from the first serveur ,we have all devices files about all Luns .

And when we do an ioscan from the second serveur ( backup ) we have the same devices files about all those luns .

please give us all the steps to do a restore all the configuration and volumes groupes using the second serveur ( backup ) if the first one fail ,with out risks for the data costumer.

Using for example vgimport with a mapfile created before in the first serveur , or doing a vgcfgbackup with files in /etc/lvmconf existing in the first serveur .

thanks for the help.

best regards.

Re: Exporting and importing volumes groupe to an other serveur

James Murtagh — Wed, 26 Mar 2003 10:28:08 GMT

Hi,

I can give you an example how to import one volume group to another server. However, note there are several other things you should consider:

Kernel parameters - make sure they are the same on both servers
/etc/fstab - this will need to be updated to reflect the new filesystems
Startup scripts - you will need any application scripts copied over and linked as normal

These are just things off the top of my head, there may be more.

This is an example of importing vg01 to another server. You wouldn't use vgcfgbackup/vgcfgrestore as you are talking about the same disks - they already have the LVM information on them!

1) Check the minor number of the group file on the primary server

# ll /dev/vg01/group

2) Create a map file and outfile of the disks, to save you entering them all in the vgimport

# vgexport -p -v -m /tmp/vg01.map -f /tmp/disks.map vg01

3) Transfer the mapfiles to the secondary server

4) Make the vg01 directory and group file

# mkdir /dev/vg01
# mknod /dev/vg01/group c 64 0x010000

0x010000 should be the same as you found from step one, keeps everything aligned.

5) Import the VG

# vgimport -v -m /tmp/vg01.map -f /tmp/disks.map vg01

Regards,

James.

Re: Exporting and importing volumes groupe to an other serveur

Pete Randall — Wed, 26 Mar 2003 11:11:11 GMT

Just a couple of comments on James' well thought out and well documented procedure. In step 2, the export in preview mode, I would use the -s option rather than -f: "vgexport -p -s -m /tmp/vg01.map vg01". Then, in step 5, when you actually import the volumes, I would use the -s option again: "vgimport -s -m /tmp/vg01.map vg01".

It's a subtle difference but proven to work, for me, at least.

Pete

Re: Exporting and importing volumes groupe to an other serveur

James Murtagh — Wed, 26 Mar 2003 11:32:34 GMT

Hi Pete,

Yeah, wasn't sure if that only worked with S/G, the "Series 800 Only" warning in the man page put the suspicion in my mind! I also couldn't test on my workstation. I would go with that as it doesn't activate the VG.

Cheers,

James.

Re: Exporting and importing volumes groupe to an other serveur

Pete Randall — Wed, 26 Mar 2003 11:34:39 GMT

James,

It works like a charm, even in a non S/G environment!!

Cheers,
Pete

Re: Exporting and importing volumes groupe to an other serveur

Pete Randall — Wed, 26 Mar 2003 11:36:24 GMT

Oh yeah, we better add step 6, then: vgchange -a y vg01

Pete

Re: Exporting and importing volumes groupe to an other serveur

Ravi_8 — Wed, 26 Mar 2003 11:47:32 GMT

Hi,

Pete

In the step 2 which James has given -p is only for preview. it wouldn't actually export.

you need to use the step 2 without -p.

and ofcourse as we all can see after importing,
another step is needed to activate vg (vgchange -a y vg01)

Re: Exporting and importing volumes groupe to an other serveur

James Murtagh — Wed, 26 Mar 2003 11:55:46 GMT

Hi Ravi,

We don't actually want to export it, just create the map file. We just need to get the lvmtab updated and device files created on the other host.

Regards,

James.

Re: Exporting and importing volumes groupe to an other serveur

Ravi_8 — Wed, 26 Mar 2003 13:29:08 GMT

James

I agree with u

Re: Exporting and importing volumes groupe to an other serveur

Pete Randall — Wed, 26 Mar 2003 13:32:55 GMT

One more (hopefully final) thought:

You can probably do the vgimport ahead of time, leaving only the "vgchange -a y vg01" to be done at switchover, but you would want to be absolutely sure that the vgchange was NEVER run while the original server was still up and accessing the data.

Pete

Re: Exporting and importing volumes groupe to an other serveur

James Murtagh — Wed, 26 Mar 2003 13:44:58 GMT

.....which is why my first example needed refining!

Also, you will need to be very careful with the LVM startup scripts! (/etc/lvmrc & /sbin/lvmrc) If both servers are booted at the same time you are going to have problems, or any combination of one coming up while the VGs are activated and filesystems mounted on the other. You may need to disable the auto vg activation on both nodes, which means you will have to manually startup the applications/VGs every time.

S/G not looking such a bad purchase now eh? :-)