On Fri, 2007-10-12 at 10:54 -0500, Scott Marlowe wrote: > On 10/12/07, Jack Orenstein <jack.orenstein@xxxxxxx> wrote: > > Our testing involves cutting power to machines running postgres 7.4, > > while under load (lots of reads and writes). When we do this, we often > > lose some files under pg_data storing table content. I.e., the file > > named for a table's pg_class.oid value is simply gone. This can affect > > many tables following a power outage. We know this problem has > > occurred when we are unable to access a table, e.g. > > > > ERROR: relation "xxx" does not exist > > > > The table is present in the system tables, but the file storing table > > content under pg_data is missing. > > > > Can anyone provide insight on this phenomenon? Why are these files > > lost? Are they really lost, or have they simply moved somewhere? What > > happens to the disk blocks formerly occupied by the files? > > > > Getting back in service following this file loss is not a problem; I'm > > just trying to understand how postgres gets into this state. > > First of all, this should not happen on a machine with proper > fsyncing. The possible causes are generally either fsync is off in > postgresql.conf or the drive array <--> OS layer is lying about fsync > operations. What filesystem are you using? I've seen similar problems on JFS2, it was something with logredo or fsck being busted on a Big Blue OS. -- Brad Nicholson 416-673-4106 Database Administrator, Afilias Canada Corp. ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
