> 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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