From: | Pól Ua Laoínecháin <linehanp(at)tcd(dot)ie> |
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To: | Ron <ronljohnsonjr(at)gmail(dot)com> |
Cc: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: PostgreSQL, Asynchronous I/O, Buffered I/O and why did fsync-gate not affect Oracle or MySQL? |
Date: | 2021-05-04 08:41:19 |
Message-ID: | CAF4RT5TJso7QUBPhCz2bJGw2ew3h0cUiTVf_MV7K4qZYbbf=Gw@mail.gmail.com |
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Lists: | pgsql-general |
Hi Ron, and thanks for your input.
> > Now, I'm not quite sure that I completely comprehend matters: Is there
> > a difference between Asynchronous I/O and Buffered I/O?
> * Asynchronous (a-syn-chron-ous) is an adjective which means "not together with time".
> * Buffered means "read more than you need at the moment, and then do processing to/from a cache".
> Their antonyms are
> * Synchronous (syn-chron-ous): together with time.
> * Direct, where you read/write only what you need at the moment, directly to/from the IO device.
> Thus, async IO is where you tell the IO subsystem that you need something, and then go off and do something else; the IO system interrupts you when the data has been delivered.
> Synchronous IO is where you request IO and then wait for the data.
Grand - that's the conclusion I was coming to myself...
If you (or anyone) would have any good detailed technical references
which explain these issues, I'd be very grateful.
Rgs,
Pól...
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