This was a last minute request to move five databases on two servers from an old failing storage system to a new one. There was a total of 5.6 terabytes to move and the databases were in heavy use by the development team. The DBA who usually supported these systems was unavailable so I started working with the storage team to get this done.
I was able to get the storage team to create 67 new disks with the same sizes as the original disks and assign them to the correct servers. I researched how to get the disks to show up for ASM on Windows. There were 37 diskgroups and I assigned the new disks to each disk group according to the size of the original disks. So each diskgroup now had double the storage.
The next step shows the power of this technique: I dropped the old disks from each diskgroup and ASM moved all the data from the old disks to the new disks, then released the old disks. I started these late in the day and they finished the next morning. No downtime, no impact to the development team.
Lessons learned: use standard disk sizes, minimize the number of diskgroups