Date: Sun, 7 Dec 2008 06:41:10 -0600 (CST) From: Wes Morgan <morganw@chemikals.org> To: Peter Schuller <peter.schuller@infidyne.com> 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. Message-ID: <alpine.BSF.2.00.0812070640100.22265@ibyngvyr.purzvxnyf.bet> In-Reply-To: <20081207113509.GA19385@hyperion.scode.org> References: <20081117205526.GC1733@garage.freebsd.pl> <20081202203308.GA13818@hyperion.scode.org> <200812021254.21242.fjwcash@gmail.com> <20081202232924.GA19134@hyperion.scode.org> <31C70CBC-488A-4A9A-A642-37855E8F1DD1@lassitu.de> <C0D30482-40E1-40FE-81FB-7029D235C264@bsdunix.ch> <b649e5e0812040302o53a979d8nb3dda3eeda0ccf8f@mail.gmail.com> <20081207113509.GA19385@hyperion.scode.org>
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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?
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