Re: no universally correct setting for fsync

Michael Tharp wrote:
> On 05/08/2010 04:07 AM, Craig Ringer wrote:
> > It's probably worth mentioning that people who want to turn off fsync to
> > gain a performance boost should instead look at a RAID controller with a
> > BBU so they can safely enable write-back caching, getting most of the
> > benefits of fsync=off safely.
> 
> Which options specifically should be set if a BBU is in use? Obviously 
> fsync should be on always, but can full_page_writes be disabled? Are 
> there other tweaks that can be done?
> 
> It would be great to see some practical hints in the documentation while 
> the fsync part is getting changed.

Uh, our docs have:
Turning this parameter off speeds normal operation, but mightlead to a corrupt database after an operating system crash
orpowerfailure. The risks are similar to turning off<varname>fsync</>, though smaller.  It might be safe to turnoff
thisparameter if you have hardware (such as a battery-backeddisk controller) or file-system software that reduces the
riskofpartial page writes to an acceptably low level (e.g., ZFS).
 

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com