Re: WALWriter active during recovery

On 2014-12-16 16:12:40 +0200, Heikki Linnakangas wrote:
> On 12/15/2014 08:51 PM, Simon Riggs wrote:
> >Currently, WALReceiver writes and fsyncs data it receives. Clearly,
> >while we are waiting for an fsync we aren't doing any other useful
> >work.
> >
> >Following patch starts WALWriter during recovery and makes it
> >responsible for fsyncing data, allowing WALReceiver to progress other
> >useful actions.
> 
> What other useful actions can WAL receiver do while it's waiting? It doesn't
> do much else than receive WAL, and fsync it to disk.

It can actually receive further data from the network and write it to
disk? On a relatively low latency network the buffers aren't that
large. Right now we generate quite a bursty IO pattern with the disks
alternating between idle and fully busy.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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