On Apr 27, 2013, at 10:40 AM, Yang Zhang wrote: > My question really boils down to: if we're interested in using COW > snapshotting (a common feature of modern filesystems and hosting > environments), would we necessarily need to ensure the data and > pg_xlog are on the same snapshotted volume? If not, how should we be > taking the snapshots - should we be using pg_start_backup() and then > taking the snapshot of one before the other? (What order?) What if > we have tablespaces, do we take snapshots of those, followed by the > cluster directory, followed by pg_xlog?
We do this, using xfs to take advantage of being able to freeze the filesystem. (Because we're also using software raid.) The process looks like: 1. pg_start_backup() 2. xfs_freeze both the data and xlog filesystems. 3. snapshot all volumes. 4. unfreeze 5. stop backup
