subvolume / folder compression flag

subvolume / folder compression flag

[Ali AlipourR]

Hi,

1- Do setting compression flag per subvolume is implemented?
(I did read on wiki that it is not implemented, but I can set it via
"btrfs  property")

2- If I set compression flag via "btrfs property" or "chattr" on a
subvolume, and rsync files without compression flag from ext4 file
system and preserve attributes by rsync -AX, do these files on that
btrfs subvolume will be compressed?
I mean do files will be compressed even if their compression flag
wasn't set, and just their subvolume compression flag was set?

3- what if I do same as 2 but on normal folder instead of subvolume
(chattr +c that folder), Do files within that folder will be
compressed even if their compression flag wasn't set?

Thanks,
Ali

Re: subvolume / folder compression flag

[Robert White]

On 12/13/2014 06:59 PM, Ali AlipourR wrote:

> 2- ... and rsync files without compression flag ...

The --compress flag for rsync has nothing to do with how the files are 
stored on either end. It determines whether the data is compressed as it 
passes from the source rsync to the destination rsync process over the 
network or whatever.

I don't have any information about the rest of the question but the 
rsync option doesn't change the data as read or written, just as 
transmitted.

The only difference between using compressed or not is:

source --normal--> rsync --compressed--> rsync --normal--> dst
source --normal--> rsync --not_compressed--> rsync --normal--> dst

If the fielsystems at source or dst do transparent compression then that 
will be done/undone transparently.

Re: subvolume / folder compression flag

[Austin S Hemmelgarn]

[-- Attachment #1: Type: text/plain, Size: 1423 bytes --]

On 2014-12-13 21:59, Ali AlipourR wrote:
> Hi,
>
> 1- Do setting compression flag per subvolume is implemented?
> (I did read on wiki that it is not implemented, but I can set it via
> "btrfs  property")
AFAIK, it's the compression related mount options that don't work 
per-subvolume.  Using chattr +c or btrfs properties should work (I don't 
know if btrfs properties are inherited by default though).
>
> 2- If I set compression flag via "btrfs property" or "chattr" on a
> subvolume, and rsync files without compression flag from ext4 file
> system and preserve attributes by rsync -AX, do these files on that
> btrfs subvolume will be compressed?
> I mean do files will be compressed even if their compression flag
> wasn't set, and just their subvolume compression flag was set?
>
> 3- what if I do same as 2 but on normal folder instead of subvolume
> (chattr +c that folder), Do files within that folder will be
> compressed even if their compression flag wasn't set?
These depend on many things.  Using -A won't (barring bugs in rsync) 
affect anything set by either chattr or btrfs properties.  Using -X 
MIGHT clear the btrfs properties, but I don't think it affects stuff set 
by chattr unless you are root (I know that it doesn't preserve 
immutability or append-only flags unless you are root).  In both 2 and 
3, I believe that the files will be uncompressed on the btrfs volume.


[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 2455 bytes --]