btrfs Question

**roly33** · May 6th, 2013

Does btrfs use Disk Compression or has the About This Computer gone a bit screwed up in the 13.10 Development Release, as About This Computer is saying that my 250GB HDD is a 500.1GB HDD?

Screenshot from 2013-05-06 18:44:37.jpg

Roland

**Cheesemill** · May 6th, 2013

Btrfs does have the ability to use compression, but it isn't enabled by default. I doubt you would get that level of compression out of it anyway.
What's the output of....

Code:

sudo parted -l

**roly33** · May 6th, 2013

Originally Posted by Cheesemill

Btrfs does have the ability to use compression, but it isn't enabled by default. I doubt you would get that level of compression out of it anyway.
What's the output of....

Code:

sudo parted -l

This is the output of sudo parted -l

roland@steelers:~$ sudo parted -l
[sudo] password for roland:
Model: ATA Hitachi HTS54502 (scsi)
Disk /dev/sda: 250GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start End Size Type File system Flags
1 1049kB 250GB 250GB primary btrfs boot

roland@steelers:~$

Roland

**grahammechanical** · May 6th, 2013

As regards my system. I would say that Details should be recording the size (approximately) of the partition it is installed upon and not the whole hard disk. In my case I have Saucy in 21GB ( / ) and 27GB (/home) and Details is showing 47.3GB. That is why I say approximately. Ext4, by the way.

Regards

**Cheesemill** · May 6th, 2013

I'm getting the same behaviour as always on my machine, the total size of all installed drives...

Screenshot from 2013-05-06 20:16:36.jpg

I'm using LVM + ext4 on my drives so it looks like this is only an issue with btrfs. Do you just have a simple btrfs setup or are you using any of the advanced features? I can imagine that creating a snapshot of a 250GB partition may cause the issue you are seeing if it appears as two seperate 250GB drives to the system.

**Rukiri** · May 7th, 2013

Originally Posted by roly33

Does btrfs use Disk Compression or has the About This Computer gone a bit screwed up in the 13.10 Development Release, as About This Computer is saying that my 250GB HDD is a 500.1GB HDD?

Screenshot from 2013-05-06 18:44:37.jpg

Roland

Okay, did you at any point do btrfs device add /xxx/xxxx / ?
I've used btrfs for quite awhile and I've never seen this much compression, also I would refrain from using lvm (it's slow... at R/W even on my SSDs)

**jerrylamos** · May 7th, 2013

I don't know anything about btrfs (!). On a mulit-partition setup with Pangolin, Windows 7, etc. I tried specifying btrfs on a saucy install and promptly got a couple abends. One message indicated a problem with another partition not even the one I was installing to.

Ext4 worked fine.

**roly33** · May 7th, 2013

Originally Posted by Cheesemill

I'm getting the same behaviour as always on my machine, the total size of all installed drives...

Screenshot from 2013-05-06 20:16:36.jpg

I'm using LVM + ext4 on my drives so it looks like this is only an issue with btrfs. Do you just have a simple btrfs setup or are you using any of the advanced features? I can imagine that creating a snapshot of a 250GB partition may cause the issue you are seeing if it appears as two seperate 250GB drives to the system.

I've just got 1 Partition / with no /swap or /home partitions.

Originally Posted by Rukiri

Okay, did you at any point do btrfs device add /xxx/xxxx / ?
I've used btrfs for quite awhile and I've never seen this much compression, also I would refrain from using lvm (it's slow... at R/W even on my SSDs)

I just created the single btrfs partition using the Something Else option in the Installer, my Daily Build Disk wouldn't let me Install properly through just the Installer so I had to Install from the Live Session, if that could have caused this?

I'm not to bothered as it's not effecting anything, unless Toshiba have used a 500GB HDD and limited it to 250GB and only btrfs sees the rest (not even sure that's possible with SATA, but I know PATA HDDs can be limited through Jumper settings).

Roland

**IanW** · May 7th, 2013

ISTR Grub may have issues if /boot is on a btrfs partition.

Originally Posted by Ubuntu Documentation

As of 11.04, it is possible to use only btrfs file systems with the caveat that grub 'MUST NOT' be installed to the boot sector of the btrfs volume containing /boot.
See also Ubuntu Grub2 Bug 757446 and Ubuntu Grub2 Bug 759772. You must install it to either the parent (sda rather than sda1; MBR/Reserved Sectors) 'OR' use
a dedicated /boot partition as described in this forum post.

When installing Ubuntu in one large btrfs-Partition without an extra boot-partition, take care to keep about 1 Mib space free at the beginning of the disk.
This is possible using the partition manager in the Ubuntu installer. When there is not this space, the installer fails at the end when trying to install Grub!

https://help.ubuntu.com/community/btrfs

**roly33** · May 8th, 2013

Originally Posted by IanW

ISTR Grub may have issues if /boot is on a btrfs partition.

https://help.ubuntu.com/community/btrfs

Strange as I'm not having any problems with Grub, just HDD gaining an extra 250.1GB.

What are the best Partition Sizes e.g size of /boot, /swap, /home & / for a 250GB HDD with 3.7GB of System RAM (using the Ubuntu Installer numbers as I can never work out the MB & GB sizes with the long number format that the Installer uses)?

Roland