On Jul 16, 2009, at 12:07 AM, Heikki Linnakangas wrote:
Dimitri Fontaine wrote:
Le 15 juil. 09 à 23:03, Heikki Linnakangas a écrit :
Furthermore, the counter-argument against having the primary
able to send data from the archives to some standby is that it should
still work when primary's dead, but as this is only done in the setup
phase, I don't see that being able to continue preparing a not-yet-
ready
standby against a dead primary is buying us anything.
The situation arises also when the standby falls badly behind. A
simple
solution to that is to add a switch in the master to specify "always
keep X MB of WAL in pg_xlog". The standby will then still find it in
pg_xlog, making it harder for a standby to fall so much behind that it
can't find the WAL it needs in the primary anymore. Tom suggested that
we can just give up and re-sync with a new base backup, but that
really
requires built-in base backup capability, and is only practical for
small databases.
If you use an rsync like algorithm for doing the base backups wouldn't
that increase the size of the database for which it would still be
practical to just re-sync? Couldn't you in fact sync a very large
database if the amount of actual change in the files was a small
percentage of the total size?
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