As we all know, downtime is an unavoidable must in some cases. There may be cases when the application need to be migrated to a new system, and it can only be done offline. Even if the downtime can’t be eliminated, you can do some things to minimize it.
First, create the new filesystem layout on the new system, set the ownership and permission of every mount points. In case of a clustered environment, install a new HA package just similar to the old one. After that, you should use rsync to copy the source to its new place, this with the application running on the source machine. Don’t be afraid of corrupted data, this is why we use rsync!
So, in this step the majority of the data was already transferred to the destination server. After that, just stop the application, and do an rsync again. Rsync uses an algorithm which provides a very fast method for bringing remote files into sync. It does this by sending just the differences in the files, optionally with compression. So, with the second rsync the application was stopped, this ensures that the data is consistent. With this step only the changed data will be transferred to the new server, and it takes much less time than that required for migrating the whole data offline. If you finished with the migration, you can start the application on the new server.
rsync is downloadable from the HP-UX Porting Center, but you can also get it with the Internet Express DVD for free.
