# btrfs - missing alot of space

## Simba7

I've just noticed this, but it seems I'm missing some space on my servers.

Svr1: /dev/sda3              1651724    169140    678588  20% /mnt/gentoo

Svr2:rootfs               4393957356   2868884 4388833100   1% /

Svr3:rootfs               5858800620    881260 5855547708   1% /

Svr4:rootfs               5858800620    764584 5855646328   1% /

Svr5:rootfs                70958060    894472  67690536   2% /

Just wondering what the heck is going on. I'm using kernel 2.6.38 and btrfs (w/zlib compression, compress-force).

----------

## Letharion

I suggest you check out the Btrfs FAQ (https://btrfs.wiki.kernel.org/index.php/FAQ) which among other things states that "Free space is a tricky concept in Btrfs", probably meaning there's not a really short answer to your question  :Smile: 

(The faqs seems down at the moment, check googles cache)

----------

## Simba7

Ya.. After a bit of reading, it's the metadata info.

Damn.. does it get bigger as the HDD space gets larger?

----------

## Letharion

 *Simba7 wrote:*   

> Ya.. After a bit of reading, it's the metadata info.
> 
> Damn.. does it get bigger as the HDD space gets larger?

 

I can't answer that in detail, but btrfs is _not_ here to make the most use of your space. It's supposed to make your data safe. I think we can expect harddrives to be significantly smaller with btrfs.

----------

## idella4

Simba7;

this is old news. I use a couple of btfs sub folders for portage.

https://forums.gentoo.org/viewtopic-t-838367-highlight-devsk.html

https://bugzilla.kernel.org/show_bug.cgi?id=16508

https://btrfs.wiki.kernel.org/index.php/

also peruse the ongoing thread in the forum sub cat gentoo-chat for much more. Be careful!!

----------

## Simba7

 *idella4 wrote:*   

> also peruse the ongoing thread in the forum sub cat gentoo-chat for much more. Be careful!!

 

Roger that.

Anyway, I found that if you just use the flag "-m single" during mkfs.btrfs, it won't create DUP. This should save quite a bit on wasted space.

----------

## Simba7

 *Simba7 wrote:*   

> Anyway, I found that if you just use the flag "-m single" during mkfs.btrfs, it won't create DUP. This should save quite a bit on wasted space.

 

Not as much as I thought, though. I'm still having issues with running out of disk space. *sigh*

----------

## pigeon768

2.6.37 introduced mixed block groups. This is supposed to reduced space overhead on small disks.

The trouble is, I don't know how to go about enabling this functionality. Does anyone else know?

----------

