On Thu, Sep 27, 2012 at 12:44:27PM +0200, Sébastien Maury wrote:
> I've installed a new server using btrfs for my root partition ("/").
>
> It uses snapper for snapshots management and all seems to work pretty fine.
>
> My problem is to be able to know the remaining REAL free space in my
> partition.This is in the FAQ: https://btrfs.wiki.kernel.org/index.php/FAQ#Why_are_there_so_many_ways_to_check_the_amount_of_free_space.3F Short answer: you can't know in general. Longer answer -- see below. > Using different commands, i have different results, and i don't know > how to interpret them correctly : > poivron:~ # btrfs filesystem show /dev/sda3 > Label: none uuid: 9e68b667-f9f9-490f-9da1-ae4e91558212 > Total devices 1 FS bytes used 2.58GB > devid 1 size 131.64GB used 10.04GB path /dev/sda3 You have 131.64 GiB of raw storage in your filesystem. Of that, 10.04 GiB is currently allocated for use by the FS (and it will take more as it needs it). > poivron:~ # btrfs filesystem df / > Data: total=4.01GB, used=2.16GB 4.01 GiB of the 10.04 GiB allocation is assigned for use by data, and 2.16 GiB of that allocation actually contains data. > System, DUP: total=8.00MB, used=4.00KB 16 MiB (=2*8.00 MiB) of the 10.04 GiB allocation is assigned for use as two copies of the system data. There is 4 KiB of system data actually used. > System: total=4.00MB, used=0.00 > Metadata, DUP: total=3.00GB, used=429.16MB 6 GiB (=2*3.00 GiB) of your 10.04 GiB allocation is assigned for use as metadata, with two copies (DUP) being kept. 429.16 MiB of the 3.00 GiB is currently in use. > Metadata: total=8.00MB, used=0.00 > poivron:~ # df -hP / > Filesystem Size Used Avail Use% Mounted on > /dev/sda3 132G 3.0G 124G 3% / Plain old df can't handle the truth, so this is at best only a hint at what's actually happening. When "Avail" reaches zero, your FS is probably full. Other than that, you can't necessarily say very much. > =========== > > Please help me understand and interpret those information to know the > most accurately as possible what is my real remaining space, and what > space is used by what. > > Although, i don't really understand the output of the command "btrfs > filesystem df /" : what are exactly "Data", "System DUP", "System > total", "Metadata DUP" and "Metadata total" ? This should all be covered in the glossary on the website: https://btrfs.wiki.kernel.org/index.php/Glossary Data is the contents of your files. Metadata is all the other stuff that the FS needs in order to store your files -- directory structures, permissions, locations of the file data, that kind of thing. System is a particular bit of the metadata (the chunk tree) which governs an internal physical/virtual mapping, and which needs to be read before anything else can make any kind of sense. DUP is a bit like RAID-1: anything stored in a DUP chunk is actually written to two different places on the disk, and can help recovery in the case of physical disk corruption (e.g. bad blocks, head crash). > ========== > > Here are some complementary informations : > poivron:~ # uname -a > Linux poivron 3.0.26-0.7-default #1 SMP Tue Apr 17 10:27:57 UTC 2012 > (3829766) x86_64 x86_64 x86_64 GNU/Linux You [probably(*)] need to upgrade your kernel as soon as possible. btrfs code moves very fast, and 3.0 has significant bugs in it. You should be running the latest released kernel -- right now, that's 3.5, or 3.6-rc7. Next week, it will probably change to 3.6 when Linus makes the next release. Most distributions have a repository somewhere which will give you access to new kernels without too much trouble. Hugo. (*) Some of the enterprise distributions do have backported btrfs fixes in their apparently older kernels. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- __(_'> Squeak! ---
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