Date: Tue, 21 Jun 2011 18:46:45 +1000 From: Peter Jeremy <peterjeremy@acm.org> To: Kirk McKusick <mckusick@mckusick.com> Cc: freebsd-fs@freebsd.org, Jeff Roberson <jroberson@chesapeake.net> Subject: Re: SU+J: negative used diskspace (for a while) Message-ID: <20110621084645.GA68018@server.vk2pj.dyndns.org> In-Reply-To: <201106171842.p5HIgQjn018296@chez.mckusick.com> References: <20110617153415.GA92803@testsoekris.hotsoft.nl> <201106171842.p5HIgQjn018296@chez.mckusick.com>
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--lrZ03NoBR/3+SXJZ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2011-Jun-17 11:42:26 -0700, Kirk McKusick <mckusick@mckusick.com> wrote: >> Date: Fri, 17 Jun 2011 17:34:15 +0200 >> From: Hans Ottevanger <hans@beastielabs.net> >> So it takes more than a minute before the disk space is back to "normal" >> values. >We used to account for deleted blocks at the instant that they were >removed. This accounting was rather complex, so as part of doing >SU+J, Jeff simplified it. Under the simplification, the removal is >not accounted for until part way through the removal process. The >result is that you now get these false negative block counts until >the blocks have been partially reclaimed. If this behavior causes >enough trouble, Jeff might be convinced that the more accurate block >accounting is necessary. Negative values may also impact NFS clients - though just limiting the reported used space to 0 should avoid them getting too upset. That said, whilst I haven't seen negative used values, ZFS and Solaris UFS also take an extended period before 'df' reports correct values (several minutes for Solaris UFS). In the case of ZFS, even 'du' can report incorrect information for a while. --=20 Peter Jeremy --lrZ03NoBR/3+SXJZ Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (FreeBSD) iEYEARECAAYFAk4AWnUACgkQ/opHv/APuIecHgCdEPSaZIABGsfWByKiNV6jlg2A 7SoAoMNHZQsYAjdgV+R9cs/vQ/udpXBX =Ddxw -----END PGP SIGNATURE----- --lrZ03NoBR/3+SXJZ--
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