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Thu, 21 Mar 2019 08:59:43 -0700 (PDT) Received: from localhost ([5.172.255.168]) by smtp.gmail.com with ESMTPSA id 15sm1027449lft.88.2019.03.21.08.59.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Mar 2019 08:59:43 -0700 (PDT) Subject: Re: Question about ext4 extents and file fragmentation To: Theodore Ts'o Cc: linux-ext4@vger.kernel.org References: <20190321031833.GB32021@mit.edu> <20190321150520.GE9434@mit.edu> From: Mikhail Morfikov Openpgp: preference=signencrypt Autocrypt: addr=mmorfikov@gmail.com; prefer-encrypt=mutual; keydata= mQINBFKDi0gBEADqBkwR00qrGmRq2rPM8g4LMBbLbYBtZLzFXpO+GB4sq47vZ0iq6BNwfRQG JMpHo3rYCekleN7Qqbszwt18QTCP/8aMFx6g6CcfKVmdgyoRwlGPa6YSJlFOuH3JvSFyttyT gFcyfyAJrl2aSXq5bjiyND5RuoLW5mlovfgq1YBFNg6arCo4I5h0EYVvWmKv++5CFaGg3q9W GzFpFkmJiHGlg/Wu/xP4GNZJbou07z/Y51JScw5s3KOped8ltM52ZXcVCT3eUdc6g4zX9MTS agkVo5vb7TlGPuW0LTdqsUk+dXgZo3w5NipbgU1kU6P4cxKy1XHwdSpQ/2j3zMoaW0NMIeYC o24mQkO3fJiLIAgNKq+CUwZgXkKfpkYL3QJOJkn+OwjsAJmcIhbU1Dp//JPmPUZIEGE/9gE3 K7USmb2v9hoMh9VUfe/W3AS7mFwuOPwyl8IKoVPvD7X1vIGYTv4Z4sKR4yRwW7FehfeiwafU Y8Wov6nMJ+TeS1wucc+4wy/R1GoGIaUur2y/S4G40MA5hQKzRUQ2caqDxrW7tbACxsEzgWRi Dbrlpwg9FHcOi5iwQcs0pwQmhmG5Go9SszPA/oTQIsv/tBRyTZjIlDMsHD7KwhRFTXLS3PMq cQpBt62OCEty3bO7EI4Ndbhx6k2qpJulKN3/YOXiSBA0IC7SiwARAQABtDJNaWtoYWlsIE1v cmZpa292IChzZWNvbmRhcnkpIDxtbW9yZmlrb3ZAZ21haWwuY29tPokCVwQTAQoAQQIbAwIe AQIXgAULCQgHAwUVCgkICwUWAgMBAAIZARYhBOSTz1puQu0xQ1DKqc0EaBB3G2UgBQJcXUQ1 BQkLuuxtAAoJEM0EaBB3G2Ug908QAKZ9WUWLcipmHJHMqn/R108KMIzOwvDUs5UcrY6Cjd03 X1sd45VO4DdBGmi2y4v+ziO+iAQB0BaJKr3d7ILUUA/QD3NXx9HgnXI9g1MFouqf/idTy+iH Nxx36v4zwnFN9BZWsx4zjMSVSh0gZsvHvpCeFvGwNVSW2cWUR73b5lE59pNR+AALFAY1KkFc IKM2lrkcDY4xsvuT4tqBy5t3/dzrkyuAMxlZxQiPtTRTHwWh/KlF1ZCyQrdCUjhjbQfXoi+U gQu/sXjEeOeA2n7Jv9RX8ZvghGuKawxogZhvETObXBubzImI/k+iZmibZye4b1yxaQ5naQXp i5iBWwTzVJK8Os/T/ScbSgDDTZIB9dic8pcie/EzDWYUWyxEzc6/OsOFjb8N3LLqc4JUyLK/ X+xgLXvp5dQEhy24b1oXb3LuIyDhDJgzmXMqqCr3cXq0N7sxkNKGI9L6f279YiEsq9+i3bVa +kdUZtbZwQKTWOrQ/DANZ1qlA0TiXTOx+aoVCjr9w70s33eFhv740zImWQnclqC3hjxUn0iA 5AKirgm95xEKqCeEKTdSg2h1rIgj3hlE1shqRuiA9BMQdRXpNh03w40x/CrCw2L3RXcf3LWe 2XxSK3EYDptLWt0lN7R2Btz3hi/7QfU6K8k1RYaXnl63+Vybg4xLkXvzzkkcE+6duQINBFKD i0gBEADKPLX2vMQgwmAUbMDJc8jIjFrHqNOeiMLT2NpVqP4mYbsIeUsGERH6XpMeoSr3v4cs R3dw6kE+OBT5DqztyzpnPVOKENsXpcncKPhviM2DpWizfpwymDB+80vjYaNVJ272iyBFVlD/ wCfCQVF3TFgPS4suEx4+02+cZ/whP1oCasllIrSpiCLMGCLFI0Hrn4mZtZB8scZQBLhDRuT8 ebKUKGakxMuqYxWpElX6VsUUl25vGuBlnjAPdwJSK7WYhyAAYu3zTxEOafJGaRCnX5lu0td4 DFvUmWDEUYRN/xiyCanHrwK+gyCiM3D+5NRVqi4vB5xV+ZZHbyDd69m7nTRQI8IqfFfdEFms Vicfyyh8t3pwNeOs9OulMXA6heBKsgNBxSRfFewzlpkIHIMuyiyejySnAsr9wzHu5ZyfNPb1 HVfPLMRJ0WTsrPcn3xE367OrdLX8ZOCAcsJXZL7dMRLLyIARam92bLa8f9VBJbwHZRABnfgP pO/sphgyFL8I8bMWAnQQHcIYU7KuXV7lS2U23ockrl5SPr7YklFDNVgq9n+eq270AUkX14Yx aHr3tKrgVbuYlaz5BAxZvZNALit4cL5zSOwDTeegYZlV4DXXoS6SFJzv+E4jZ6iYC8X8Im6Q s/Rqjsi6TVMYE4vV+hdBEFzTSJM3da2WKiDqpaNI4QARAQABiQI8BBgBCgAmAhsMFiEE5JPP Wm5C7TFDUMqpzQRoEHcbZSAFAlxdRJsFCQu67NMACgkQzQRoEHcbZSBlKw//TYPt68ZkcSV/ vjim+QvsTLOLtY1hzB5zIlz7viIOlBuTl6btI/QDPxE2HxgiIi1g+inB32p3uJQzfYpTvK+Y c8ItwiPXhIwdTWNhlzS1iXoVQdj9jJUlM2Y91KtratRtAQcwgWOSe2pl1KrQoVctBwRE4Bbs PONiJlaaEyjZIrdfGcj1dURm0C0iLkEG/Le1VvQxS9mKWnoIWnxTyle5cN44a06hUmDWVuqX l3uQr9E4mRvxVkAN4dItftVhpeCe0oZcxDGKFiBguRD2SCq0h/gQfQGUyApo1KsrH9C7ny+Z tOvUHCEIM9PlGmqA8lFVj+P5gbcUfW5Duqu0D5NPWLGhIfLSCxg8LGFd9GPC2UxYt4aCuS02 0MKhEHsHfg7c2avqfQ9xK0l8ZrROax0gdniz2lPkSdB+S6Z9XqamgGbZnXYU1dJaM2r35tOd YfVgG9nf7g2bxCa9wmYdBR2ZDri5o6Pwd76xAp5J5W9GCfiY0uH5qfy4899JxLNgEx7PheZ6 0x69Z+hTiaMv3+9mY24G/KmwnOnYDp/0lVdTczGzozD9xYaG4ReP/gS2TQMKwEto8IEX336C Bj+Sti8AiDaBCrnhCERxAbYwJTbtTP05fg5u/JorJfD6L76A2wHn9il1yJ4/HAJgs7KGevUg VyIzwTcJuLgTKoPQBcfsUkg= Message-ID: Date: Thu, 21 Mar 2019 16:59:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190321150520.GE9434@mit.edu> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="0CQslNEktQ03I0Tdzk8zN80nzu56XiWbQ" Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --0CQslNEktQ03I0Tdzk8zN80nzu56XiWbQ Content-Type: multipart/mixed; boundary="F2dwoE7XqK1AQQupyKxcTfG0bCPqW1hMR"; protected-headers="v1" From: Mikhail Morfikov To: Theodore Ts'o Cc: linux-ext4@vger.kernel.org Message-ID: Subject: Re: Question about ext4 extents and file fragmentation References: <20190321031833.GB32021@mit.edu> <20190321150520.GE9434@mit.edu> In-Reply-To: <20190321150520.GE9434@mit.edu> --F2dwoE7XqK1AQQupyKxcTfG0bCPqW1hMR Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 21/03/2019 16:05, Theodore Ts'o wrote: > It *could* be read sequentially from the beginning of the file to the > end. There are many things that might cause that not to happen, that > have nothing to do with how we store the logical to physicla map. And this is what I wanted to know, because some people tell that if you=20 store a file in a filesystem, it can't be read sequentially as a whole=20 because of the filesystem layer (compared to "dd if=3D/dev/sda ..."). So = the filesystem layer doesn't really matter and doesn't really add any=20 additional delays compared to the raw read of a device when we deal with = data that is stored in contiguous blocks. I know that many things can=20 prevent the sequential read from happening, but I just wanted it to be=20 clarified.=20 Thank you for the answer, I really appreciate it. --F2dwoE7XqK1AQQupyKxcTfG0bCPqW1hMR-- --0CQslNEktQ03I0Tdzk8zN80nzu56XiWbQ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE5JPPWm5C7TFDUMqpzQRoEHcbZSAFAlyTtOwACgkQzQRoEHcb ZSAiihAAv1/G2ZphjsZ2aVwCnTjazcEc8OxWLf0K4tpr+3vxjjDPR59ENyD/YQjf rCrJgyJR9ahu/A17PonwcFUPduVtqr2KeFvwztqlpaIr1o9zT1hAoPX8TQN1+dy+ MGgi8gsePRdOCynb4gkTYiFPU+/NKVueN6bDl14/Ud+oB7Dh42FtJphG3Z96wdsr DY5lvAlb5Zrkx3aBK/TxKHvT2MmTGEEkJVxmYj/D5+ZZlegr8xO3qFdVbYn/l/W9 9vBjad9+1oIr7dOl1OxPtMJ3TZ25gBsFIx+Rg3a11QOjH0AvpX1v7YvTwCAcGwcG I3tCY1pT+DAeXXoTOIAShWts+YI9wXjwZOIVH6z+kU98Isi2BPsl/3Mr6Hk4EqAX x2CGc9cn/jf8v+HJ4Xk9Ddah9AK+ETG/xizYoOysOrL31QSFiFfJSxSdNy2t20S1 mzP9fQ8KSREJOPbXKPlRNVMqQBu91eM+Uky7Tq8064xGVow1ULV3l0dwR7K94nAS nsYkDTsqcdGFLL2uGcLL8dLHowwFqbAyyq7Uj1iS+vo4+GgejmroZnXzpMnEfiKu BNUT4zM/lpCwVkNMH4OYqp5NIE6zWhULQhRrvUheLHf2BMDH5qEZ4E395aPoeKZz dLCXuaeu1DIZtnJKPDGvlaYWM+emoFTlRz/csan7yNtrs01GrQU= =4UPo -----END PGP SIGNATURE----- --0CQslNEktQ03I0Tdzk8zN80nzu56XiWbQ--