Re: Recomended FS

Got to going this today, after a small delay due to the arrival of new 
disks,

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.
>
>  
>