David Garamond wrote: > Bruce Momjian wrote: > > David Garamond wrote: > > > >>Is there a feature similar to this currently in Postgres, or will there > >>be? Sometimes (like in a shared hosting environment), we cannot have the > >>luxury of hot-swapped RAID or expensive SAN, and it's nice to be able to > >>have a synchronous backup so that in case a disk fails, we can recover > >>to the last moment just before failure. > >> > >>Will PITR offer this? > > > > Pitr recovers from the last moment before failure. Not sure what > > shadowing is. > > Sorry, should've at least described 'shadowing'. A shadow is a > synchronous page-level (I think) mirror file. That is, when you open a > database /disk1/dbname.fdb and then issue a: > > > CREATE SHADOW 1 '/disk2/dbname.fdb'; > > CREATE SHADOW 2 '/disk3/dbname.fdb'; > > then all 3 files will be kept synchronized at all times. Each subsequent > page write will go to all 3 files (if any of the write fails, the > transaction fails, so it's not unlike a synchronous replication). > > Now suppose /disk1 fails, one of the shadow can be configured to > immediately take over as the master database, without any down time. We > can then add /disk4/dbname.fdb, for instance, to become a new shadow. > > Alternatively, when a shadow fails, IB/Firebird can refuse further > transactions until there is another shadow coming up, so the database is > shadowed all the time. No, we don't have plans to do that. We will allow continuous logging so a tar backup plus this log will bring you up to current. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
