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From: webmaster@zedlx.com
To: Qu Wenruo <quwenruo.btrfs@gmx.com>, linux-btrfs@vger.kernel.org
Subject: Re: Feature requests: online backup - defrag - change RAID level
Date: Tue, 10 Sep 2019 21:00:23 -0400
Message-ID: <20190910210023.Horde.FW3TNKclQrm7CjBRGG_NPNO@server53.web-hosting.com> (raw)
In-Reply-To: <20190910202637.Horde.sP3Q7-sjETTnnOXgETzjAZX@server53.web-hosting.com>


Quoting myself webmaster@zedlx.com:

> B) "sharing-defrag"
>    a file is share-defragmented if ALL of the following are met:
>    1) all extents are written on disk in neighbouring sectors in the  
> ascending order
      2) all pairs of *adjanced* extents meet AT LEAST ONE of the  
following criteria
>       2.1) both extents are sufficiently large
>       2.2) the two extents have mismatching sharing groups (they are  
> shared by different sets of files)

If it is hard to undersztand what is meant by those rules, consider  
the following example (copy-pasted from previous post):

Let's say that there is a file FFF with extents e11, e12, e13, e22,
e23, e33, e34
- in subvolA the file FFF consists of e11, e12, e13
- in subvolB the file FFF consists of e11, e22, e23
- in subvolC the file FFF consists of e11, e22, e33, e34

After defrag, where 'selected subvolume' is subvolC, the extents are
ordered on disk as follows:

e11,e22,e33,e34 - e23 - e12,e13

In the list above, the comma denotes neighbouring extents, the dash
indicates that there can be a possible gap.

As you can see in the list, the file FFF is fully sharing-defragmented in
subvolC, since its extents are occupying neighbouring disk sectors.  
Except for extents e33,e34  which can be fused if one of them is too  
small. If that is not the case (e33,e34 are sufficiently large), then  
the perfect solution is given.


  parent reply index

Thread overview: 111+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09  2:55 zedlryqc
2019-09-09  3:51 ` Qu Wenruo
2019-09-09 11:25   ` zedlryqc
2019-09-09 12:18     ` Qu Wenruo
2019-09-09 12:28       ` Qu Wenruo
2019-09-09 17:11         ` webmaster
2019-09-10 17:39           ` Andrei Borzenkov
2019-09-10 22:41             ` webmaster
2019-09-09 15:29       ` Graham Cobb
2019-09-09 17:24         ` Remi Gauvin
2019-09-09 19:26         ` webmaster
2019-09-10 19:22           ` Austin S. Hemmelgarn
2019-09-10 23:32             ` webmaster
2019-09-11 12:02               ` Austin S. Hemmelgarn
2019-09-11 16:26                 ` Zygo Blaxell
2019-09-11 17:20                 ` webmaster
2019-09-11 18:19                   ` Austin S. Hemmelgarn
2019-09-11 20:01                     ` webmaster
2019-09-11 21:42                       ` Zygo Blaxell
2019-09-13  1:33                         ` General Zed
2019-09-11 21:37                     ` webmaster
2019-09-12 11:31                       ` Austin S. Hemmelgarn
2019-09-12 19:18                         ` webmaster
2019-09-12 19:44                           ` Chris Murphy
2019-09-12 21:34                             ` General Zed
2019-09-12 22:28                               ` Chris Murphy
2019-09-12 22:57                                 ` General Zed
2019-09-12 23:54                                   ` Zygo Blaxell
2019-09-13  0:26                                     ` General Zed
2019-09-13  3:12                                       ` Zygo Blaxell
2019-09-13  5:05                                         ` General Zed
2019-09-14  0:56                                           ` Zygo Blaxell
2019-09-14  1:50                                             ` General Zed
2019-09-14  4:42                                               ` Zygo Blaxell
2019-09-14  4:53                                                 ` Zygo Blaxell
2019-09-15 17:54                                                 ` General Zed
2019-09-16 22:51                                                   ` Zygo Blaxell
2019-09-17  1:03                                                     ` General Zed
2019-09-17  1:34                                                       ` General Zed
2019-09-17  1:44                                                       ` Chris Murphy
2019-09-17  4:55                                                         ` Zygo Blaxell
2019-09-17  4:19                                                       ` Zygo Blaxell
2019-09-17  3:10                                                     ` General Zed
2019-09-17  4:05                                                       ` General Zed
2019-09-14  1:56                                             ` General Zed
2019-09-13  5:22                                         ` General Zed
2019-09-13  6:16                                         ` General Zed
2019-09-13  6:58                                         ` General Zed
2019-09-13  9:25                                           ` General Zed
2019-09-13 17:02                                             ` General Zed
2019-09-14  0:59                                             ` Zygo Blaxell
2019-09-14  1:28                                               ` General Zed
2019-09-14  4:28                                                 ` Zygo Blaxell
2019-09-15 18:05                                                   ` General Zed
2019-09-16 23:05                                                     ` Zygo Blaxell
2019-09-13  7:51                                         ` General Zed
2019-09-13 11:04                                     ` Austin S. Hemmelgarn
2019-09-13 20:43                                       ` Zygo Blaxell
2019-09-14  0:20                                         ` General Zed
2019-09-14 18:29                                       ` Chris Murphy
2019-09-14 23:39                                         ` Zygo Blaxell
2019-09-13 11:09                                   ` Austin S. Hemmelgarn
2019-09-13 17:20                                     ` General Zed
2019-09-13 18:20                                       ` General Zed
2019-09-12 19:54                           ` Austin S. Hemmelgarn
2019-09-12 22:21                             ` General Zed
2019-09-13 11:53                               ` Austin S. Hemmelgarn
2019-09-13 16:54                                 ` General Zed
2019-09-13 18:29                                   ` Austin S. Hemmelgarn
2019-09-13 19:40                                     ` General Zed
2019-09-14 15:10                                       ` Jukka Larja
2019-09-12 22:47                             ` General Zed
2019-09-11 21:37                   ` Zygo Blaxell
2019-09-11 23:21                     ` webmaster
2019-09-12  0:10                       ` Remi Gauvin
2019-09-12  3:05                         ` webmaster
2019-09-12  3:30                           ` Remi Gauvin
2019-09-12  3:33                             ` Remi Gauvin
2019-09-12  5:19                       ` Zygo Blaxell
2019-09-12 21:23                         ` General Zed
2019-09-14  4:12                           ` Zygo Blaxell
2019-09-16 11:42                             ` General Zed
2019-09-17  0:49                               ` Zygo Blaxell
2019-09-17  2:30                                 ` General Zed
2019-09-17  5:30                                   ` Zygo Blaxell
2019-09-17 10:07                                     ` General Zed
2019-09-17 23:40                                       ` Zygo Blaxell
2019-09-18  4:37                                         ` General Zed
2019-09-18 18:00                                           ` Zygo Blaxell
2019-09-10 23:58             ` webmaster
2019-09-09 23:24         ` Qu Wenruo
2019-09-09 23:25         ` webmaster
2019-09-09 16:38       ` webmaster
2019-09-09 23:44         ` Qu Wenruo
2019-09-10  0:00           ` Chris Murphy
2019-09-10  0:51             ` Qu Wenruo
2019-09-10  0:06           ` webmaster
2019-09-10  0:48             ` Qu Wenruo
2019-09-10  1:24               ` webmaster
2019-09-10  1:48                 ` Qu Wenruo
2019-09-10  3:32                   ` webmaster
2019-09-10 14:14                     ` Nikolay Borisov
2019-09-10 22:35                       ` webmaster
2019-09-11  6:40                         ` Nikolay Borisov
2019-09-10 22:48                     ` webmaster
2019-09-10 23:14                   ` webmaster
2019-09-11  0:26               ` webmaster
2019-09-11  0:36                 ` webmaster
2019-09-11  1:00                 ` webmaster [this message]
2019-09-10 11:12     ` Austin S. Hemmelgarn
2019-09-09  3:12 webmaster

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