| From: | Ben Chobot <bench(at)silentmedia(dot)com> |
|---|---|
| To: | Konrad Garus <konrad(dot)garus(at)gmail(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | [SPAM] Re: shared_buffers advice |
| Date: | 2010-05-24 15:27:43 |
| Message-ID: | A2662635-A15D-4B71-B551-DC4020561DF9@silentmedia.com |
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| Thread: | |
| Lists: | pgsql-performance |
On May 24, 2010, at 4:25 AM, Konrad Garus wrote:
> Do shared_buffers duplicate contents of OS page cache? If so, how do I
> know if 25% RAM is the right value for me? Actually it would not seem
> to be true - the less redundancy the better.
You can look into the pg_buffercache contrib module.
> Another question - is there a tool or built-in statistic that tells
> when/how often/how much a table is read from disk? I mean physical
> read, not poll from OS cache to shared_buffers.
Well, the pg_stat_* tables tell you how much logical IO is going on, but postgres has no way of knowing how effective the OS or disk controller caches are.
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