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Wed, 07 Aug 2024 00:51:05 +0200 Message-ID: <05767a39-e59c-4615-b693-774976bd54f1@gmx.com> Date: Wed, 7 Aug 2024 08:21:02 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: 'btrfs filesystem defragment' makes files explode in size, especially fallocated ones To: Hanabishi , linux-btrfs@vger.kernel.org References: <7a85ea4e-814f-4940-bd3e-13299197530f@gmx.com> <90dab7d5-0ab8-48fe-8993-f821aa8a0db8@gmail.com> <0f6cc8e0-ab32-4792-863e-0ef795258051@gmx.com> <837fb96f-989c-4b56-8bd4-6f8fb5e60e7d@gmail.com> <62433c69-5d07-4781-bf2f-6558d7e79134@gmail.com> <30687f37-32e9-4482-a453-7451ab05277a@gmail.com> <55a368af-ab0b-4bb8-b61b-53d20b163d63@gmx.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00iVQUJDToH pgAKCRDCPZHzoSX+qNKACACkjDLzCvcFuDlgqCiS4ajHAo6twGra3uGgY2klo3S4JespWifr BLPPak74oOShqNZ8yWzB1Bkz1u93Ifx3c3H0r2vLWrImoP5eQdymVqMWmDAq+sV1Koyt8gXQ XPD2jQCrfR9nUuV1F3Z4Lgo+6I5LjuXBVEayFdz/VYK63+YLEAlSowCF72Lkz06TmaI0XMyj jgRNGM2MRgfxbprCcsgUypaDfmhY2nrhIzPUICURfp9t/65+/PLlV4nYs+DtSwPyNjkPX72+ LdyIdY+BqS8cZbPG5spCyJIlZonADojLDYQq4QnufARU51zyVjzTXMg5gAttDZwTH+8LbNI4 mm2YzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00ibgUJDToHvwAK CRDCPZHzoSX+qK6vB/9yyZlsS+ijtsvwYDjGA2WhVhN07Xa5SBBvGCAycyGGzSMkOJcOtUUf tD+ADyrLbLuVSfRN1ke738UojphwkSFj4t9scG5A+U8GgOZtrlYOsY2+cG3R5vjoXUgXMP37 INfWh0KbJodf0G48xouesn08cbfUdlphSMXujCA8y5TcNyRuNv2q5Nizl8sKhUZzh4BascoK DChBuznBsucCTAGrwPgG4/ul6HnWE8DipMKvkV9ob1xJS2W4WJRPp6QdVrBWJ9cCdtpR6GbL iQi22uZXoSPv/0oUrGU+U5X4IvdnvT+8viPzszL5wXswJZfqfy8tmHM85yjObVdIG6AlnrrD In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:pgDEqhUPcLExup0QjUDH5gG/9DiRQ2yA4oBM9Ai/svyvLF2Ogzg JqGBDfRT/lDdJ8jOyytS+ZWRngXnQ7dD8eZRnrfJhG7YivlQYI4XoQapZILItuvrGLF5V29 580VLzvXT3qSffMEiaxKRVljsIKrbqUUnBJTYu2UAptCpSzgXlz0un70GoKfIq5Am+ReYUt s/S+Nvp84KyPgQmsvoYLg== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:O6DbS6PLv+8=;z42MyIVJDyzI3HCI8y2H+ggHM9o 4HsF7AvTeRVg0H3Ji6jRNK+lJLZ40JJVWwb5oKcoQB4iss4dUFde3exImClezz9RE3h9kzcN5 hvGVF4BrZf4K12Ua8EOF49sdXRt1aBh+ievVLB5Wvx550aTCFkXGa2Xu0UXFhIdnb4HDFgzpq 8BGPRGLZYkUxjz2UcVCt7AmaiGKsx1gTZaKHJwxYeW0I4Z9ZZdY1Jo/CnhJ0PrvzxeaqSXy5I RFh3l2YoS0lXxUZp9GdZUwUIULt8hKRNS2QDQc1KDCvlQRb9GYgKdA0EuT2KKRVUUT5CSjR/0 XRZA0Sgq9fo5st4ukpE50QzLj3eTaekDZs9HStrvef7JeLl2OeLp2QPysgv6rJjYF3CFYQzXT e1VOhy1DMRkmltTeOR0Qz1tXyed3WnvSr85yBGWgmS9BiHxyeo7snUZxsjuB62TgnoAQrhz1g Q57mZXczNEZ/1eRaQZP9fIXL6KuqncF309ZUov+7MndEilw9OqpsVF2EOyrIztCosZUq9E7r3 GIHUUOtHfKIebYik0MoSzjwYBG0jEaRxtiqbzDOMulK+6DAVfiU/9ce8WSS+JG0hvBU7twcXw 1HGZfx6bh04ibr432UReh6QnIDgL7oemTohGUFEXEXtIeSz8JMu02tuIqLFKu8oxjvwaxlJa4 2cReP8vWCbhEVRtGFRnLMrKkzjAoHDEeMSR16k8kjycYe6J4Tm3pojdE63Wq8Vib2qlXCV9yR EGqjY51QTTQLF/M5GJ15TKbyV0uwHG/gbLfC90Ny7Tf96ypZx0Mw99gP2P3WvRRDiwD8vzRrj mHD8TDnoqQcEP6Wpn6UQ63bw== =E5=9C=A8 2024/8/7 08:12, Hanabishi =E5=86=99=E9=81=93: > On 8/6/24 22:10, Qu Wenruo wrote: > >> But you're using btrfs for its super fast snapshot, and that will force >> data COW, causing all the complexity. > > For me the data checksumming is more of a selling point. I.e. yes, using > Btrfs in a NOCOW mode kinda defies the point. In that data csum (and COW) case, then I guess one has to choose if preallocation is really wanted very carefully. Or it's super easy to cause unexpected on-disk space waste. (COW is already going to cause space waste, but preallocation amplifies that much faster) > >> It means, even you have written 10GiB new data, as long as our >> transaction is not committed, you will only get all the old data after = a >> power loss (unless it's explicitly fsynced). >> That's another point very different from old non-COW filesystems. >> >> Instead "commit=3D" with a lower value is more helpful for btrfs, but t= hat >> would cause more metadata writes though. > > What about "flushoncommit" mount option? Does it make data view more > resilient? > If combined with lower commit=3D value, yes, it will be data view more consistent with transactions. But as usual, it amplifies the metadata writes, which is already pretty bad for btrfs. And may worse the extra space usage problem too, if using data COW (as it forces dirty pages writeback at every transaction commit, causing smaller writes) (I guess a UPS would be better for everyone except the budget?) Thanks, Qu