Clustering Without MCServiceGuard

[ahpux]

I wish to connect a disk system to 2 servers. The file systems need to be mounted on only one server at a time. If the server 1 goes down, i will mount the file systems manually on the server 2. The name of the VG will be kept same on both the servers. I wont be using MCServiceGuard.
Has anybody tried this out?

[Zygmunt Krawczyk]

It is correct solution. You don't need MC/SG for this functionality.
Regards,
Zygmunt

[Romaric Guilloud]

Yes it works out of any MC/SG consideration.
The only thing it to mount in exclusive mode the vg in order to prevent data corruption from both sides.
To achive this:
vgchange -a e

Rgds,
Romaric.

[Marek Smejkal]

Hi,

If your disk system is SCSI you have to change controller address (7) of the second system to (6).
When you want to mount the second system you have to usually run fsck.

Marek

[ahpux]

How should i do vgexport, as i want to keep the information available on both the servers?

[Steve Lewis · Accepted solution]

You cannot vgchange -a e without buying and installing MC/SG. This is the critical functionality that protects your data. Its one reason why this configuration isn't supported by HP. You need to be absolutely sure that you cannot overwrite any on the other system. Of course you can overwrite/destroy anyway, by bypassing LVM, but people generally use LVM.
Do not try to mount any filesystem on both systems at once, unless you either mount read-only on both, or cross-mount using NFS.

vgexport -m /tmp/vgNN.map -p -v /dev/vgNN
Use -p to vgexport in preview mode, which does not destroy the data. Make a note of your disk paths. tar your /dev/vgNN directory and copy that across.

[ahpux]

I had to create PVGs so as to suit the requiremenents . Will it be necessary to create the /etc/lvmpvg file on both the servers and then use the vgexport -p -s -m mapfile /dev/vgXX and then do a vgimport on the server 2?

[Sridhar Bhaskarla]

Hi,

PVG is nothing but a flat file in /etc called lvmpvg. After you imported the VGs, just copy the file from the other server into /etc directory and modify it to suit to the disk device files on this server. Only "c#" may change.

Also one *very important* thing to note is to modify your /etc/lvmrc file to ensure that these VGs are not automatically activated during the boot. Specify other VGs for activation in this file. Do not have these VGs activated on the other node while the application is running.

However, it is best to use ServiceGuard to avoid any issues. May cost some money but it's worth if you need availability.

-Sri