On Sun, Dec 7, 2014 at 11:34 AM, Hugo Mills <h...@carfax.org.uk> wrote:
> *Any* value shown here is going to be inaccurate, and whatever way > round we show it, someone will complain. Yeah I'd suggest that for regular df command, when multiple device volumes exist, they're shown with ?? for Avail and Use% columns. Maybe one day df can show more columns: AvailS/R0, AvailR1, AvailR5, AvailR6. Today: # btrfs fi show Label: 'test' uuid: fb7df1f2-480d-4426-84f1-8aed197700e4 Total devices 2 FS bytes used 1.38GiB devid 1 size 5.00GiB used 2.28GiB path /dev/loop0 devid 2 size 5.00GiB used 2.28GiB path /dev/loop1 # df -h Filesystem Size Used Avail Use% Mounted on /dev/loop0 5.0G 1.4G 4.0G 27% /mnt # btrfs fi df /mnt Data, RAID1: total=2.00GiB, used=1.38GiB System, RAID1: total=32.00MiB, used=16.00KiB Metadata, RAID1: total=256.00MiB, used=1.61MiB GlobalReserve, single: total=16.00MiB, used=0.00B Perhaps something like this instead: # btrfs fi df /mnt Available Space Range: 5.4GiB - 7.2 GiB RAID0 Available: ~5.1GiB Data: allocated=1.0GiB, used=0.1GiB System: allocated=32MiB, used=16KiB Metadata:allocated=256MiB, used=KiB RAID1 Available: ~2.7GiB Data: allocated=2.00GiB, used=1.38GiB System: allocated=32.00MiB, used=16.00KiB Metadata: allocated=256.00MiB, used=1.61MiB SINGLE Available: GlobalReserve: allocated=16.00MiB, used=0.00B 1. There's 10.0GiB of total space for two devices in the volume. 2. There's 1.3GiB raid0 chunks allocated, and 4.6GiB raid1 chunks allocated, 5.6 GiB is allocated. 3. To show available space for any particular profile, we have to subtract out all the allocated chunks, and then add back in the free space only for that profile's chunks. 4. The resulting value needs to be multiplied by that profile's "replication factor" e.g. 1 for single and raid0, 0.5 for raid1, and for raid 5/6 it depends not just on the number of devices, but the mix of chunks striped across n disks since Btrfs allows chunks to be striped across any number of disks so long as it meets the minimum, i.e. there can be a dozen raid5 chunks striped across 3 drives, and another 1/2 dozen chunks striped across 4 drives. Only a balance would redistribute such that each chunk has the same number of strips. For above it's raid0 available: [10.00 total - 5.9 allocated + the free space in only raid0 chunks] * 1 raid1 available: [10.00 total - 5.9 allocated + the free space in only raid1 chunks] * 0.5 -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
