Re: Compression of full-page-writes

On 2013-09-11 12:43:21 +0200, Andres Freund wrote:
> On 2013-09-11 19:39:14 +0900, Fujii Masao wrote:
> > * Benchmark
> > pgbench -c 32 -j 4 -T 900 -M prepared
> > scaling factor: 100
> >
> > checkpoint_segments = 1024
> > checkpoint_timeout = 5min
> > (every checkpoint during benchmark were triggered by checkpoint_timeout)
> >
> > * Result
> > [tps]
> > 1344.2 (full_page_writes = on)
> > 1605.9 (compress)
> > 1810.1 (off)
> >
> > [the amount of WAL generated during running pgbench]
> > 4422 MB (on)
> > 1517 MB (compress)
> > 885 MB (off)
> >
> > [time required to replay WAL generated during running pgbench]
> > 61s (on) .... 1209911 transactions were replayed,
> > recovery speed: 19834.6 transactions/sec
> > 39s (compress) .... 1445446 transactions were replayed,
> > recovery speed: 37062.7 transactions/sec
> > 37s (off) .... 1629235 transactions were replayed,
> > recovery speed: 44033.3 transactions/sec
>
> ISTM for those benchmarks you should use an absolute number of
> transactions, not one based on elapsed time. Otherwise the comparison
> isn't really meaningful.

I really think we need to see recovery time benchmarks with a constant
amount of transactions to judge this properly.

Greetings,

Andres Freund

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Andres Freund http://www.2ndQuadrant.com/
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