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#1 2021-11-01 21:09:29

Nan123
Member
Registered: 2021-01-24
Posts: 83

btrfs with mounted EXT4 drives

Dumb little question to ask, I just enabled zstd compression on my root drive for btrfs and am currently compressing all my current files, I am wondering how it will handle ext4 drives mounted on /mnt. Will it not touch them at all? I deceded to unmount them before the compression to be safe but I am paranoid and want to be sure it won't touch them in the future, i.e: making a new file there.
Thanks.

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#2 2021-11-01 21:12:30

loqs
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Registered: 2014-03-06
Posts: 18,993

Re: btrfs with mounted EXT4 drives

The ext4 filesystems will only use mount options passed to them.  Options on other filesystems are not used.

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#3 2021-11-01 21:13:47

Nan123
Member
Registered: 2021-01-24
Posts: 83

Re: btrfs with mounted EXT4 drives

loqs wrote:

The ext4 filesystems will only use mount options passed to them.  Options on other filesystems are not used.

So the btrfs won't touch them? Just wanted to be sure.

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#4 2021-11-01 21:15:38

loqs
Member
Registered: 2014-03-06
Posts: 18,993

Re: btrfs with mounted EXT4 drives

Nan123 wrote:
loqs wrote:

The ext4 filesystems will only use mount options passed to them.  Options on other filesystems are not used.

So the btrfs won't touch them? Just wanted to be sure.

Correct.

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#5 2021-11-01 21:27:28

Nan123
Member
Registered: 2021-01-24
Posts: 83

Re: btrfs with mounted EXT4 drives

loqs wrote:
Nan123 wrote:
loqs wrote:

The ext4 filesystems will only use mount options passed to them.  Options on other filesystems are not used.

So the btrfs won't touch them? Just wanted to be sure.

Correct.

One more question, how does this affect performance? Is there a way to use a lesser compression ratio with zstd? it downsized 16 GB to about 6 and my system feels slower, is there any way to decompress files, or to make the compression ratio less?

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#6 2021-11-01 21:35:26

loqs
Member
Registered: 2014-03-06
Posts: 18,993

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#7 2021-11-01 21:57:39

Nan123
Member
Registered: 2021-01-24
Posts: 83

Re: btrfs with mounted EXT4 drives

it seems you can't recursively uncompress a directory, how do I fix this? Am I gonna have to reinstall to remove it?

Last edited by Nan123 (2021-11-01 22:11:08)

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#8 2021-11-01 22:10:52

loqs
Member
Registered: 2014-03-06
Posts: 18,993

Re: btrfs with mounted EXT4 drives

What was the error?  Were you actually using the option [Compession level]?
As it is the root filesystem moving all data to a different filesystem and back again is none trivial.
Hopefully someone more familiar with btrfs will have a better solution.

Last edited by loqs (2021-11-01 22:11:06)

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#9 2021-11-01 22:13:15

Nan123
Member
Registered: 2021-01-24
Posts: 83

Re: btrfs with mounted EXT4 drives

loqs wrote:

What was the error?  Were you actually using the option [Compession level]?
As it is the root filesystem moving all data to a different filesystem and back again is none trivial.
Hopefully someone more familiar with btrfs will have a better solution.

I would imagine that decompressing wouldn't be much more difficult than compressing, and the fact that you can't is kinda nuts. I might just reinstall as I've only been on this install a few days.

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