SAN Storage & Server for Oracle Replication

There is no need to copy the files - there is an ASM "trick" that does exactly what you want to do with no interruption in service. When ASM rebalances a disk, it maintains a list of viable LUNS for each block independently of the LUN on which it presently lives. It also won't drop a disk on which there are active blocks without rebalancing elsewhere - but it will mark it as not a viable home for rebalancing!

Once you have used oracleasm to make the new LUNs visible to ASM, you just issue the single command (forgive syntax, off the top of my head)

alter diskgroup my_dg add disk 'new1', 'new2', 'new3' drop disk old1, old2, old3;

Then sit back and wait. ASM will hot-relocate each block from the old storage to the new, laying them out nicely on the way, and drop the old disks when the operation completes. I/O will be a bit higher, but your users probably won't notice a thing.

As for your ORACLE_HOME, I'm afraid switching that will require a (brief) outage.

Well theoretically you can issue the command "alter tablespace begin/end backup". Before and after you execute rsync. You will also need a backup copy of the control file. This approach was used many years ago before RMAN was introduced. The restore really requires Oracle experience. This approach is for example described in this book: "Unix Backup and Recovery".

A really recommend you to get familiar with RMAN. Even if you do not use backup agent like TSM/Netbackup you can still create local disk backups using RMAN and then you can synchronize this storage using rsync.