[Linux-cluster] Linux-cluster Digest, Vol 70, Issue 9

[Thomas Sjolshagen]

On Feb 9, 2010, at 9:27 AM, Bob Peterson wrote:

> ----- "Muhammad Ammad Shah" <mammadshah at hotmail.com> wrote:
> | Hi Bob,
> | 
> | if we are running Database (oracle) on GFS on two node cluster, and if
> | node(x) fenced, so this mean that there will be two problems.
> | 
> | 
> |     1. The node(x) File system (ext3) /, /var/, /usr,.... can be
> | crashed
> |     2. if the insertion was being running, then its lost.
> | 

And that is no different than if the power was lost (and the UPS backup failed).

Oracle is designed to address unexpected power loss. That's what the rollback & redo logs (in part) are for (and the use of transactions in the applications, to group logical updates/inserts/deletes so as to ensure the database is in a predictable/expected state following a failed transaction).


> | if i am right on this then its big problem to setup power fencing in
> | critical environments. i think it should be some thing different like
> | SAN data path fencing.
> | 

Not really. SAN data path fencing would result in an IO error (after the DB IO timeout is exceeded) and thus the insert/update/delete fails or is only partially completed. Once again, the Oracle transactional and/or rollback/redo functionality would restore the database files to the point where the transaction register is 'complete'.


> | one more thing i want to know, if (oracle)node was running it was
> | accessing the trace logs, control logs and ..... of oracle, then
> | node(x) fenced and node(y) starts will it read from the old
> | transaction point or it will be something else (i am not expert of
> | oracle) .

All of the above goes out the window if you're hosting your data files on a file system without support for direct-IO or you've disabled directIO (and not enabled synchronous IO) in the init.ora configuration file (by default you have to take positive action to do so for modern releases or the Oracle RDBMS software).