Date: Wed, 20 Mar 2013 14:02:04 +0100 From: "Ronald Klop" <ronald-freebsd8@klop.yi.org> To: freebsd-fs@freebsd.org Subject: Re: FreBSD 9.1 and ZFS v28 performances Message-ID: <op.wt8w5qwj8527sy@ronaldradial.versatec.local> In-Reply-To: <20130320124501.GA60926@neutralgood.org> References: <1DD6360145924BE0ABF2D0979287F5F4@multiplay.co.uk> <51474F2F.5040003@contactlab.com> <E106A7DB08744581A08C610BD8A86560@multiplay.co.uk> <51475267.1050204@contactlab.com> <514757DD.9030705@contactlab.com> <A9C89C979F8D4CBABE73256A1C66E95D@multiplay.co.uk> <alpine.GSO.2.01.1303192036240.11141@freddy.simplesystems.org> <4930f6fddf6a995051bc6554d1a6a6b7@sys.tomatointeractive.it> <51499351.1040406@digsys.bg> <op.wt8vr5c38527sy@ronaldradial.versatec.local> <20130320124501.GA60926@neutralgood.org>
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On Wed, 20 Mar 2013 13:45:01 +0100, <kpneal@pobox.com> wrote: > On Wed, Mar 20, 2013 at 01:32:19PM +0100, Ronald Klop wrote: >> On Wed, 20 Mar 2013 11:45:37 +0100, Daniel Kalchev <daniel@digsys.bg> >> wrote: >> >> Well, after changing the recordsite property, I copied the file from >> an >> >> UFS partition (using cp -Rp): this should use recordsize=16k, right? >> > >> > Perhaps, if you delete the file, or preferably the entire ZFS dataset >> > first. Copying an file over another existing, does not change anything >> > with the destination file except it's contents and modification times. >> > As is always with changing settings, it is safer to just create the >> > entire data set from scratch, with the new settings. >> > >> > Daniel >> >> ZFS never overwrites contents of a files. It always allocates new >> blocks. > > True but not really relevant. > > Taking an existing file, truncating it to length zero, and then putting > data into it results in the same file having different contents. But > deleting the existing file, creating a new file, and putting data into it > gives you (like I said) a new/different file. This is true with both UFS > and ZFS. > > Applications don't care that ZFS does COW under the hood. Applications > care that the observed behavior of ZFS be similar to UFS. > It is relevant. After changing the recordsize all new blocks will get the new recordsize. The discussion was not about if a file is the same one or not. It is about if the recordsize changes. And recreating the volume/pool is not needed for that. Ronald.
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