Re: recovery from media failure

On Fri, 2 Feb 2001, adb wrote:

> Is there any way to have up to the minute recovery from a disk
> failure in postgres?
RAID1? :)

> Is there a timeframe for the recover from WAL feature?
If you are asking if WAL logs can be reapplied to an database dump, the
answer is currently no. I think it'd be a great idea though.

One problem there is that WAL is very low-level currently. I.E. it details
'page modified, data modified'. When you restore from pg_dump, your pages
will look totally different from the moment you dumped.

You can try to solve it using a lvm snapshot to backup raw files, MAYBE
it'll just work. But, we'll need to have a switch that will turn WAL
delete-old-log-on-checkpoint off, and leave deletion to your backup tool..

Vadim, comments? What'd happen if I start postgres using database files
snapshotted at one point, PLUS all WAL write-ahead files? Would it realize
it needs to reapply WAL? Is the "list of WAL files" kept somewhere or
it'll look on disk for all files named *.chk?

-alex