Re: Losing records when server hang

Scott Marlowe wrote:

On Mon, 2004-08-09 at 09:07, lec wrote: 

Scott Marlowe wrote:    

On Sun, 2004-08-08 at 21:26, Alvaro Herrera Munoz wrote:      

On Sun, Aug 08, 2004 at 08:36:36PM -0600, Scott Marlowe wrote:          

On Sun, 2004-08-08 at 19:43, lec wrote:              

If I commit the following records 1,2,3,4,5,6,7,8,9,10 to the database 
and the server hangs, I could lose records 5,6,7,8,9 but record 10 is 
there.  How is this possible and do anyone know how Postgresql 
physically writes the records?                  

Assuming a properly function storage subsystem and a kernel that does
not lie about fsync, this is not possible.              

I'm using Redhat 7.3, kernel 2.4.18   

It is actually possible if he uses several backends to do the job, and
transaction inserting record 10 commits before the hang, and 5,6,7,8,9
don't.          

Just 1 backend.   

Yeah, but he explicitly said he'd committed 1 through 10.  Unless he
didn't understand what is meant by commit.  I.e. committing AND
receiving the ack for that commit.  Until the database says it
committed, nothing's been committed, so he might have thought just
firing the insert query was committing.  I hadn't really thought of that
angle.

Is that the case, lec?      

I explicitly 'COMMIT'   

If this is only one backend, then I'd love to see how did he do that.          

Me too :-)

      

That's exactly leaving me puzzled.  I don't know if it has anything to
do with the SCSI controller or hardware related stuff.  The controller
is a RAID, configured are RAID-5.   

Does that RAID controller have NON battery backed cache?

 

I'm not sure.