Re: New CRC algorithm: Slicing by 8

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От Alvaro Herrera
Тема Re: New CRC algorithm: Slicing by 8
Дата
Msg-id 20061024175147.GN26593@alvh.no-ip.org
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Ответ на Re: New CRC algorithm: Slicing by 8  (mark@mark.mielke.cc)
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mark@mark.mielke.cc wrote:

> I'm on wrong on one of these assumptions, I'm open to being educated.
> My opinion as of a few seconds ago, is that a write to a single disk
> sector is safe, but that a write that extends across several sectors
> is not.

Unless it's fsync'ed, which is what we do at CHECKPOINT.  Keep in mind
that we save full page images on WAL the first time we touch the page
after a checkpoint.  This means that if a partial write occured, we will
restore it from WAL.

So it's not safe in general, but it is safe in Postgres.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.


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