Without Serviceguard, can two nodes access the shared VG?

[Hanry Zhou]

I know that SG can achieve application fail over. However, in this case, we don't mind to manually bring up the database, and application. So, I am thinking we don't need SG. All I need is to put all pieces of software on the shared disks, when one node went down, we can get back the exclusive access to the shared vg, and bring up the application on another node. Am I right? If not, why?

[Mel Burslan]

for starters, how everyone in the world will know that your system died and the other one took over, i.e., how are you going to address the relocatable ip addressing ? You need to include that into your manual failover plan.

Also you need to be very careful not to let someone play with your standby system, as they may see your data drives seen by the live node as freely available volumes and have a field day with them, causing all kinds of data corruption (this is a danger even in serviceguarded environments)

[Mohanasundaram_1]

Hi Hanry,

If you want to manually bring-up the applications to another server, then you need to address the below issues

1) IP address
2) hostname
3) importing of the VGs in this system
4) Mounting of filesystems
5) Patch level to be maintained
6) Kernel configuration
7) user database
8) Application login customisation

There can be more issues which are not mentioned above. These things may take 2-4 hours. If you are prepared for such downtime then you can go with your plan.

You need to thoroughly test this before you actually go into production with such a plan.

If I were you, I would stick to Serviceguard. It has local LAN failover feature too.

With regards,
Mohan.

[Devender Khatana]

Hi,

Yes it can be achived. But automatic application startup is not the alone benefit achived by applying service guard. You can have option of starting database manually in service guard as well. This is what we do when starting database packages in debugging mode. In debugging mode the service guard only does bind package IP, activate VG/DG's and mount's file systems.

For accessing shared disk service guard also uses same LVM commands. So should not have any problems in doing this apart from being the important feature monitoring of service guard.

Also while doing this activate VG in exclusive mode on the running node to avoid writes from the other node in any case.

HTH,
Devender

[Sandman!]

Shared access to disks is only with ServiceGuard/OPS now called "SGeRAC" software i.e both nodes can read/write simultaneously. How do you plan to share disks between two nodes?

Take a look at the link below:

http://software.hp.com/portal/swdepot/displayProductInfo.do?productNumber=T1859BA