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Re: True ACID under linux (no fsync)?

From: <bmccoy(at)chapelperilous(dot)net>
To: Postgres Users <pgsql-general(at)postgresql(dot)org>
Subject: Re: True ACID under linux (no fsync)?
Date: 2000-10-31 20:22:17
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-general
"Gary Howland (During daytime)" wrote:

> Just a quickie - I heard that linux does not have a working fsync()
> call (it has no concept of raw devices).  In other words, fsync cannot
> be used to ensure that data is on disk (try it with a floppy - it
> returns IMMEDIATELY!!! - long before the write finishes)

That's because the mounted drive is buffered in memory, so when you copy a
file, you are copying it to memory (which is very fast), and the kernel
implicitly syncs with the media when the buffer fills or when an explicit
sync is done or when it is unmounted.

If there is no working fsync (and fdatasync), why do the Linux man pages
claim it to be POSIX.1b compliant?

Can you back up your claim with actual documentation?  Saying 'I heard'
puts it in the realm of urban legendry...

Brett W. McCoy
This is the ____LAST time I take travel suggestions from Ray Bradbury!

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