btrfs subvolume mount with different options

btrfs subvolume mount with different options

[Konstantin V. Gavrilenko]

Hi list,

just wondering whether it is possible to mount two subvolumes with different mount options, i.e.

|
|- /a  defaults,compress-force=lza
|
|- /b  defaults,nodatacow


since, when both subvolumes are mounted, and when I change the option for one it is changed for all of them.


thanks in advance.

Re: btrfs subvolume mount with different options

[Timofey Titovets]

2018-01-12 20:49 GMT+03:00 Konstantin V. Gavrilenko <k.gavrilenko@arhont.com>:
> Hi list,
>
> just wondering whether it is possible to mount two subvolumes with different mount options, i.e.
>
> |
> |- /a  defaults,compress-force=lza
> |
> |- /b  defaults,nodatacow
>
>
> since, when both subvolumes are mounted, and when I change the option for one it is changed for all of them.
>
>
> thanks in advance.
>
> --
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Not possible for now.

-- 
Have a nice day,
Timofey.

Re: btrfs subvolume mount with different options

[Roman Mamedov]

On Fri, 12 Jan 2018 17:49:38 +0000 (GMT)
"Konstantin V. Gavrilenko" <k.gavrilenko@arhont.com> wrote:

> Hi list,
> 
> just wondering whether it is possible to mount two subvolumes with different mount options, i.e.
> 
> |
> |- /a  defaults,compress-force=lza

You can have use different compression algorithms across the filesystem
(including none), via "btrfs properties" on directories or subvolumes. They
are inherited down the tree.

$ mkdir test
$ sudo btrfs prop set test compression zstd
$ echo abc > test/def
$ sudo btrfs prop get test/def compression
compression=zstd

But it appears this doesn't provide a way to apply compress-force.

> |- /b  defaults,nodatacow

Nodatacow can be applied to any dir/subvolume recursively, or any file (as long as it's created but not
written yet) via chattr +C.

-- 
With respect,
Roman

Re: btrfs subvolume mount with different options

[Konstantin V. Gavrilenko]

Thanks, chattr +C is that's what I am currently using.
Also you already answered my next question, why it is not possible to set +C attribute on the existing file :)


Yours sincerely,
Konstantin V. Gavrilenko


----- Original Message -----
From: "Roman Mamedov" <rm@romanrm.net>
To: "Konstantin V. Gavrilenko" <k.gavrilenko@arhont.com>
Cc: "Linux fs Btrfs" <linux-btrfs@vger.kernel.org>
Sent: Friday, 12 January, 2018 9:37:49 PM
Subject: Re: btrfs subvolume mount with different options

On Fri, 12 Jan 2018 17:49:38 +0000 (GMT)
"Konstantin V. Gavrilenko" <k.gavrilenko@arhont.com> wrote:

> Hi list,
> 
> just wondering whether it is possible to mount two subvolumes with different mount options, i.e.
> 
> |
> |- /a  defaults,compress-force=lza

You can have use different compression algorithms across the filesystem
(including none), via "btrfs properties" on directories or subvolumes. They
are inherited down the tree.

$ mkdir test
$ sudo btrfs prop set test compression zstd
$ echo abc > test/def
$ sudo btrfs prop get test/def compression
compression=zstd

But it appears this doesn't provide a way to apply compress-force.

> |- /b  defaults,nodatacow

Nodatacow can be applied to any dir/subvolume recursively, or any file (as long as it's created but not
written yet) via chattr +C.

-- 
With respect,
Roman
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