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I currently have a 4TB RAID 1 setup on a small, personal Linux server, which is formatted as XFS in LVM. I am interested in enabling the reflink feature of XFS, but I did not do so when I first created the filesystem (I used the defaults).

Is there a way that I can toggle the reflink feature on, without having to backup and re-create the filesystem? And if not, can I expect that feature to be implemented in the future?

TheSola10
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  • By the way, the `crc` feature is enabled, which according to the documentation is necessary to enable `reflink` – TheSola10 Jan 02 '20 at 13:26

1 Answers1

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After reading through documentation, I've found my answer:

By default, mkfs.xfs will create reference count btrees and therefore will enable the reflink feature. This feature is only available for filesystems created with the (default) -m crc=1 option set. When the option -m crc=0 is used, the reference count btree feature is not supported and reflink is disabled. -- mkfs.xfs(8) from Debian man pages

The way I understand it, reference count btrees are a feature enabled on filesystem creation (the b-tree is generated differently), which requires CRC. CRC alone being enabled does not imply reference count b-trees being enabled.
There is most likely no way to get around this requirement currently.

TheSola10
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  • By the way, if you're wondering about my personal server, I just dumped+converted everything to `btrfs`. idk what I expected when you can't even shrink an XFS partition without redumping – TheSola10 Aug 28 '20 at 13:59
  • What is the fud about here? xfs will enable reflinking by default. use xfs_bmap to examine the blocks used by a file. – user3504575 Jul 27 '22 at 14:59
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    @user3504575 It will enable reflinking _when creating a filesystem_. This question is about enabling reflinking on an _existing_ filesystem. Back when I created that filesystem, reflinking was not enabled by default. – TheSola10 Jul 28 '22 at 15:17