Thread: Re: Multiple WALs for PITR ?

Michael Kleiser <mkl@webde-ag.de> wrote on 06.10.2004, 16:29:08:
> I wan`t to use Point in Time Recovery
> I allread read http://developer.postgresql.org/docs/postgres/backup-online.html#BACKUP-ARCHIVING-WAL
>

Good!

> But I still wonder, if it is possible for PostgreSQL 8.0 to write multiple, redundant WAL-Files
> like Oracles with its redo-log-groups ?

Not currently.

That was something I considered, though in the end lacked both
implementation time and justification for.

If you can explain why you think that might be necessary, I'd be happy
to consider it for v8.1.

RAID-10 seems a good solution for me...

>
> Is threre an equivalent to Oracles "ALTER SYSTEM SWITCH LOGFILE" ?
>

Not currently.

Again, if you can say why we might want that, it can also be added -
other than "they have it, so we want it too" :-)

This is a likely addition for 8.1, since we will most likely want to
archive xlog files every N minutes, whatever the transaction rate,
allowing people to specify a maximum period of data loss - but this
seemed like an enhancement rather than a definite feature for 8.0

> Thanks
> Michael Kleiser
>

Glad you're interested. Your questions show you understand - good luck.

Best Regards

Simon Riggs

On 2004-10-06, simon@2ndquadrant.com <simon@2ndquadrant.com> wrote:
>
> Michael Kleiser <mkl@webde-ag.de> wrote on 06.10.2004, 16:29:08:
>> I wan`t to use Point in Time Recovery
>> I allread read http://developer.postgresql.org/docs/postgres/backup-online.html#BACKUP-ARCHIVING-WAL
>>
>
> Good!
>
>> But I still wonder, if it is possible for PostgreSQL 8.0 to write multiple, redundant WAL-Files
>> like Oracles with its redo-log-groups ?
>
> Not currently.
>
> That was something I considered, though in the end lacked both
> implementation time and justification for.

    WAL archival is more decoupled from WAL generation.

    You can use this to exploit more IO parallelism so that the same
disk isn't being written to and read from at the same time.

    Now, the concept of WAL groups would provide an extra level of
redundancy for your crash recovery files. On some of the cheaper sort of
systems that I've seen postgres deployed on this could be very useful.

[deletia]

--
        Negligence will never equal intent, no matter how you
attempt to distort reality to do so. This is what separates         |||
the real butchers from average Joes (or Fritzes) caught up in      / | \
events not in their control.