On Jul 26, 2013, at 4:53 PM, Pádraig Brady <P@xxxxxxxxxxxxxx> wrote: > On 07/26/2013 09:13 PM, Miloslav Trmač wrote: >> Hello all, >> with thin provisioning available, the total and free space values >> reported by a filesystem do not necessarily mean that that much space >> is _actually_ available (the actual backing storage may be smaller, or >> shared with other filesystems). >> >> If your package reports disk space usage to users, and bases this on >> filesystem free space, please consider whether it might need to take >> LVM thin provisioning into account. >> >> The same applies if your package automatically allocates a certain >> proportion of the total or available space. >> >> A quick way to check whether your package is likely to be affected, is >> to look for statfs() or statvfs() calls in C, or the equivalent in >> your higher-level library / programming language. > > Anything df(1) should do here? Example: Creating a btrfs raid1 volume from two 2TB drives, df shows it as having 4TB available: # parted -l Error: /dev/sdb: unrecognised disk label Model: ATA VBOX HARDDISK (scsi) Disk /dev/sdb: 2199GB Sector size (logical/physical): 512B/512B Partition Table: unknown Disk Flags: Error: /dev/sdc: unrecognised disk label Model: ATA VBOX HARDDISK (scsi) Disk /dev/sdc: 2199GB Sector size (logical/physical): 512B/512B Partition Table: unknown Disk Flags: # mkfs.btrfs -d raid1 -m raid1 /dev/sd[bc] WARNING! - Btrfs v0.20-rc1 IS EXPERIMENTAL WARNING! - see http://btrfs.wiki.kernel.org before using adding device /dev/sdc id 2 fs created label (null) on /dev/sdb nodesize 4096 leafsize 4096 sectorsize 4096 size 4.00TB Btrfs v0.20-rc1 # mount /dev/sdb /mnt # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 79G 4.2G 71G 6% / devtmpfs 1.5G 0 1.5G 0% /dev tmpfs 1.5G 0 1.5G 0% /dev/shm tmpfs 1.5G 680K 1.5G 1% /run tmpfs 1.5G 0 1.5G 0% /sys/fs/cgroup tmpfs 1.5G 4.0K 1.5G 1% /tmp none 224G 87G 138G 39% /media/sf_chris /dev/sdb 4.0T 56K 4.0T 1% /mnt The explanation is that the file system isn't raid1, but rather the allocated chunks have this attribute. Presently a volume only allocates with one profile, but the future plan is per subvolume and even per file raid profiles. So establishing how much free space there is on a btrfs volume is absolutely less than clear. Anyway, I think it will cause some confusion if by "available" an application thinks it can write out more than 2TB of data to this example volume. Chris Murphy -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
