Re: WAL to RAW devices ?

[Alex Vinogradovs <AVinogradovs(at)Clearpathnet(dot)com>]

Yeah, that's the trick... I need high availability with
high performance and nearly real-time synchronization ;-)
Also, I've got FreeBSD here... ZFS will be out with 7.0
release, plus UFS2 has snapshotting capability too. But
the whole method isn't good enough anyway. 


> Oh, I see.
> 
> What I've seen described is to put a PITR slave on a filesystem with
> snapshotting ability, like ZFS on Solaris.
> 
> You can then have two copies of the PITR logs.  One gets a postmaster
> running in "warm standby" mode, i.e. recovering logs in a loop.  The
> other one, in a sort of jail (I don't know the Solaris terminology for
> this) stops the recovery and enters normal mode.  You can query it all
> you like at that point.
> 
> Periodically you stop the server in normal mode, resync the snapshot
> (which basically resets the "modified" block list in the filesystem),
> take a new snapshot, create the jail and stop the recovery mode again.
> So you have a fresher postmaster for queries.
> 
> It's not as good as having a true hot standby, for sure.  But it seems
> it's good enough while we wait.
>