So the system is 2x700Mhz PIII, 512 Mb, Promise TX2000, 2x40G ATA-133 Maxtor Diamond+8 .
The relevent software is Freebsd 4.8 and Postgresql 7.4 Beta 2.
Two runs of 'pgbench -c 50 -t 1000000 -s 10 bench' with a power cord removal after about 2 minutes were performed, one with hw.ata.wc = 1 (write cache enabled) and other with hw.ata.wc = 0 (disabled).
In *both* cases the Pg server survived - i.e it came up, performed automatic recovery. Subsequent 'vacuum full' and further runs of pgbench completed with no issues.
I would conclude that it not *always* the case that power failure renders the database unuseable.
I have just noticed a similar posting from Scott were he finds the cache enabled case has an dead database after power failure. It seems that it's a question of how *likely* is it that the database will survive/not survive a power failure...
The other interesting possibility is that Freebsd with soft updates helped things remain salvageable in the cache enabled case (as some writes *must* be lost at power off in this case)....
regards
Mark
scott.marlowe wrote:
OK, but here's the real test. As the postgres user, run 'pgbench -i', then after that runs, run 'pgbench -c 50 -t 1000000'. While it's running and settled (pg aux|grep postgres|wc -l should show a number of ~54 or so.) pull the plug. Wait for the hard drives to spin down, then plug it back in and power it one. With SCSI you will still have a coherent database.
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