Hi, We've recently set up our database (7.4.9) with our new hosting provider. We have two database servers running RHEL 4 in a cluster; one active and one hot-spare. They share a [fibre-channel connected] SAN partition; the active server has it mounted. Now my question is this; the provider has, by default, mounted it with -o sync; so all reads/writes are synchronous. This doesn't result in the greatest of performance, and indeed remounting -o async is significantly faster. They tell me this is so mySQL databases don't get corrupted in the event of a crash. which is fine... But as Postgres uses fsync() to force committed transactions to disk, then this shouldn't be necessary, right? (I know this is based on the assumption the SAN doesn't lie about its syncs, but then surely it would lie to the kernel with -o sync anyway?) If we turn sync off, surely PostgreSQL keeps the data consistent, ext3 journalling keeps the filesystem clean [assuming other mount options left at defaults], and then everything should be ok with either a server crash, power failure, storage failure, whatever. right? I've googled and come up with some info; the most relevant of which is here: http://archives.postgresql.org/pgsql-general/2003-11/msg01515.php http://archives.postgresql.org/pgsql-general/2003-11/msg01592.php If anyone can confirm either way that'd be great - or even just point me in the direction of enough firm info to work it out myself ;) Thanks, Shane
