Scott Marlowe <smarlowe@xxxxxxxxxxxxxxxxx> writes: > On Thu, 2005-11-10 at 08:43, Michael Stone wrote: >> There's no reason to use a journaled filesystem for the wal. Use ext2 in >> preference to ext3. > Not from what I understood. Ext2 can't guarantee that your data will > even be there in any form after a crash. I believe only metadata > journaling is needed though. No, Mike is right: for WAL you shouldn't need any journaling. This is because we zero out *and fsync* an entire WAL file before we ever consider putting live WAL data in it. During live use of a WAL file, its metadata is not changing. As long as the filesystem follows the minimal rule of syncing metadata about a file when it fsyncs the file, all the live WAL files should survive crashes OK. We can afford to do this mainly because WAL files can normally be recycled instead of created afresh, so the zero-out overhead doesn't get paid during normal operation. You do need metadata journaling for all non-WAL PG files, since we don't fsync them every time we extend them; which means the filesystem could lose track of which disk blocks belong to such a file, if it's not journaled. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
