Re: Losing records when server hang

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.

--lec