Re: understanding postgres issues/bottlenecks

On Sat, Jan 10, 2009 at 5:40 AM, Ron <rjpeace(at)earthlink(dot)net> wrote:
> At 03:28 PM 1/8/2009, Merlin Moncure wrote:
>> just be aware of the danger . hard reset (power off) class of failure
>> when fsync = off means you are loading from backups.
>
> That's what redundant power conditioning UPS's are supposed to help prevent
> ;-)

But of course, they can't prevent them, but only reduce the likelihood
of their occurrance. Everyone who's working in large hosting
environments has at least one horror story to tell about a power
outage that never should have happened.

> I would not recommend fysnc = off if you do not have other safety measures
> in place to protect against data loss because of a power event..
> (At least for most DB applications.)

Agreed. Keep in mind that you'll be losing whatever wasn't
transferred to the backup machines.

> ...and of course, those lucky few with bigger budgets can use SSD's and not
> care what fsync is set to.

Would that prevent any corruption if the writes got out of order
because of lack of fsync? Or partial writes? Or wouldn't fsync still
need to be turned on to keep the data safe.