Date: Mon, 25 Aug 2025 13:44:51 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@FreeBSD.org> To: "Rob Norris" <robn@despairlabs.com> Cc: "Cedric Blancher" <cedric.blancher@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: NFSv4.2 READ_PLUS support? Message-ID: <861pozwrpo.fsf@ltc.des.dev> In-Reply-To: <eeb8551b-2f55-49c0-aabb-f68875495671@app.fastmail.com> (Rob Norris's message of "Mon, 25 Aug 2025 11:36:51 %2B1000") References: <CALXu0UfzyaZti2dSbZHPf_YXU88_2oCP98cXJPM6mQ9Fsr6ZuQ@mail.gmail.com> <CAM5tNy7x=AttZiu=ZLFtiQS3U2JD=gZOgjeGE-VoB1Obp9eZxQ@mail.gmail.com> <aKh3ZpxPYSIfMFfX@kib.kiev.ua> <CAM5tNy6WL93tVX18RsEUymYXON-W50i_-xm1CxrN6n0nbecmYg@mail.gmail.com> <CALXu0Uf%2B=GD8ZkZmN1v3s2GKp8Y5VDoiTO-cjay3Ypf1wmPMQw@mail.gmail.com> <eeb8551b-2f55-49c0-aabb-f68875495671@app.fastmail.com>
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"Rob Norris" <robn@despairlabs.com> writes: > Cedric Blancher <cedric.blancher@gmail.com> writes: > > Holes are not sequences of 0x00 bytes. Holes means "no data here". ZFS > > compression should preserve the sparse information, otherwise you turn > > ANY sequence of 0x00 bytes into holes,and that will break databases > > and other applications which depend on exactly that *precise* > > semantics. > This is the second time I've heard this on this list (previously[1]) but > I don't know what it's referring to. They made it up. A hole is just an optimization, and it is 100% up to the file system whether holes are created and where. Any application that considers a hole to be semantically different from a sequence of zeroes is broken. DES -- Dag-Erling Smørgrav - des@FreeBSD.orghelp
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