On Tue, Jun 20, 2017 at 06:42:58PM +0300, Sergey Burladyan wrote: > Bruce Momjian <br...@momjian.us> writes: > > > On Tue, Jun 20, 2017 at 01:10:26PM +0300, Sergey Burladyan wrote: > > > Only if missing/changed files changed in size, because rsync run with > > > --size-only it does not copy changed files with same size. > > > > I am sorry but I am not understanding. Step 10.b says: > > > > 10.b Make sure the new standby data directories do not exist > > > > Make sure the new standby data directories do not exist or are empty. If > > initdb was run, delete the standby server data directories. > > > > so the _entire_ new data directory is empty before rsync is run, meaning > > that it is an exact copy of the new master. > > Yes, new data directory at standby is empty, but you missed old data > directory at standby which is hardlink'ed by rsync into new as at master.
OK, I think I am getting closer to understanding. Only some files are hard-linked from the old master to the new master, specifically the user data files (table and indexes). > rsync run with _three_ arguments and with --hard-links option: > rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata > remote_dir > (remote_dir is parent directory for old and new data at standby) > > In this mode rsync compare not only new_pgdata with new empty data > directory at standby, but also compare it with old data directory from > standby and with --size-only it doing this compare only by the file > existence or file size. but it only going to create hard links for hard links that already exist between the old and new masters. If I am wrong, we are in big trouble because rsync would not work. > If file at standby in old data directory is different from same file at > master, but it have same size, it will be hardlinked into new data > directory at standby and does not copied from master. Only if pg_upgrade created the hardlinks, right? -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
