From: | Ron <ronljohnsonjr(at)gmail(dot)com> |
---|---|
To: | 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: | 2021-05-02 18:31:01 |
Message-ID: | 25742a94-aa0d-1595-fe0d-6931e81c1d24@gmail.com |
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Lists: | pgsql-general |
On 5/2/21 8:46 AM, Pól Ua Laoínecháin wrote:
[snip]
> 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".
They are not mutually exclusive.
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.
*Sync*hronous IO is where you request IO and then *wait for the data*.
--
Angular momentum makes the world go 'round.
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