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Date: Sun, 7 Dec 2008 06:41:10 -0600 (CST)
From: Wes Morgan <morganw@chemikals.org>
To: Peter Schuller <peter.schuller@infidyne.com>
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Cc: =?ISO-8859-15?Q?Marius_N=FCnnerich?= <marius@nuenneri.ch>,
	FreeBSD Current <freebsd-current@freebsd.org>
Subject: Re: HEADS UP: New ZFS in the tree.
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On Sun, 7 Dec 2008, Peter Schuller wrote:

>> While you are talking about it: Does anyone know if the fsync blocks
>> until the data is really stable on the device or if it simply returns
>> when ZIL is disabled?
>>
>> In my understanding the topmost block would need to be written for the
>> "commit" to be on disk.
>
> My understanding is that disabling the ZIL *will* break the semantics
> of fsync().
>
> The claim of "always consistent on disk" is not violated and is still
> maintained, since consistency refers to ZFS' internal consistency.
>
> The tuning guide someone posts a link to later in this thread has
> specific claims about this IIRC; such as NFS breaking (because
> fsync-on-close semantics mandated by NFS, among other things, will not
> be honored).

And this would also apply to databases that rely on fsync() for ACID 
compliance, such as postgres, right?