On Tue, Sep 06, 2005 at 02:58:52PM -0500, Bruno Wolff III wrote: > On Tue, Sep 06, 2005 at 13:47:42 -0500, > "Jim C. Nasby" <jnasby@xxxxxxxxxxxxx> wrote: > > On Tue, Sep 06, 2005 at 10:13:33AM -0500, Bruno Wolff III wrote: > > > On Mon, Sep 05, 2005 at 12:20:24 +0300, > > > Peter Nixon <listuser@xxxxxxxxxxxxxx> wrote: > > > > Hi List > > > > > > > > Does anyone have any comments, HOWTOs and experience running multiple > > > > Postgres servers with a shared disk (SAN) in a Hot standby configuration? > > > > > > > > Can someone please point me in the direction of any docs on this subject? > > > > > > Be sure to have some failsafe to prevent two servers from running at the > > > same time on the same data. If that ever happens your database will be hosed. > > > > I thought PostgreSQL already had such a safeguard? Or is it only against > > starting two backends against the same PGDATA on the same machine? > > Yes, but it is more likely to have problems when there are two machines > involved. One is that the file may not be on the cross mounted file > system (on FC4 it is in /var/run) and even if it is on the cross mounted > file system, there is a good chance the lock file will appear to be stale > because the process id is for the other machine. I am not sure if there are > other gotchas, but you definitely want to be careful, since a mistake is > going to defeat the purpose of having the hot spares. Maybe it would be better to keep this in PGDATA (or even a duplicate copy). Holding a write lock on the file should also help ensure that you can tell if it's stale or not. I realize this probably still isn't perfect, but it's probably better than forcing users to find an external means of locking out the other backend. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
