On Wed, Aug 6, 2014 at 12:20 PM, Bruce Momjian <br...@momjian.us> wrote: > > Well, for file-level backups we have: > > 1) use file modtime (possibly inaccurate) > 2) use file modtime and checksums (heavy read load) > > For block-level backups we have: > > 3) accumulate block numbers as WAL is written > 4) read previous WAL at incremental backup time > 5) read data page LSNs (high read load) > > The question is which of these do we want to implement? #1 is very easy > to implement, but incremental _file_ backups are larger than block-level > backups. If we have #5, would we ever want #2? If we have #3, would we > ever want #4 or #5?
You may want to implement both #3 and #2. #3 would need a config switch to enable updating the bitmap. That would make it optional to incur the I/O cost of updating the bitmap. When the bitmap isn't there, the backup would use #2. Slow, but effective. If slowness is a problem for you, you enable the bitmap and do #3. Sounds reasonable IMO, and it means you can start by implementing #2. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
