Date: Tue, 14 Jun 2011 11:06:13 -0400 From: jhell <jhell@DataIX.net> To: Per von Zweigbergk <pvz@itassistans.se> Cc: freebsd-fs@freebsd.org Subject: Re: Disk usage and ZFS deduplication Message-ID: <20110614150613.GB27199@DataIX.net> In-Reply-To: <9544F7B9-E286-4266-86E3-B4D1A667CBBD@itassistans.se> References: <9544F7B9-E286-4266-86E3-B4D1A667CBBD@itassistans.se>
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--QKdGvSO+nmPlgiQ/ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jun 14, 2011 at 09:19:32AM +0200, Per von Zweigbergk wrote: > I've been following the "Impossible compression ratio on ZFS" thread with= some interest, and it made me ask myself this: >=20 > Let us say we have a hypothetical zfs filesystem with the equally hypothe= tical files A and B. The filesystem has deduplication enabled. Both files h= ave an apparent file size of 100 MB, but 50 MB of that data is common betwe= en the two files and thus can be deduplicated. This would mean that total d= isk usage would be 150 MB. >=20 > If you use "du" to determine disk size for a deduplication, what would be= the result? Which file would the common data be accounted to? Or would it = be accounted to both files somehow, in part or in full? Logical answer would be that both files should be showing thier resulting size regardless of how ZFS processes them. Being deduped does not mean representing files to the user any different. --QKdGvSO+nmPlgiQ/ Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (FreeBSD) Comment: http://bit.ly/0x89D8547E iQEcBAEBAgAGBQJN93jkAAoJEJBXh4mJ2FR+dpIH/1c+Q47ZHLaRjqezauJ+GzWw QFyfu9AzvVxkIJDCtDuiSdp3/9l112cCOeaSpzA9MsNgjqxt2xq7TOlxBfP5wi6O 1PMNCv6geh+y/yc6nW6PVyUvzyPf4s1Lq+bWRwN+Tb12t+ttKxY/7G7Pa/M8waOm xonxaRXtCDNmGr2OpuBbo/rYpsIY6CoBuGsxwl0KM5HA+kGTvg0+MpYcsVAIodgN DliDxUKvvPMY9cu/z8vfpC58TFFUObmn9JsVYMV44+rPYW7PgBabv9LfJZ6xxJeV bpEAuxmwIc9ywCFMBU/kzsZhCwhTnKQn7XfwDJSkJCAx2pQR6jWFu1pqvrRiskA= =Cjdv -----END PGP SIGNATURE----- --QKdGvSO+nmPlgiQ/--
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