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btrfs and deduplication




Hi there,

currently iam trying to get deduplication working in debian/btrfs

#so i created a btrfs filesystem

mkfs.btrfs /dev/vdb1
mkdir /mnt/btrfs
mount /dev/vdb1 /mnt/btrfs

# create some random file
dd if=/dev/urandom of=/mnt/btrfs/img bs=1M count=1024
for i in {1..30}; do cp /mnt/btrfs/img /mnt/btrfs/img$i; done

# dedup this stuff
jdupes -S -B -r /mnt/btrfs/
Examining 31 files, 1 dirs (in 1 specified)
Deduplication done (30 files processed)

raps-debian btrfs # btrfs fi df /mnt/btrfs/
Data, single: total=31.50GiB, used=30.96GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=222.94MiB, used=33.69MiB
GlobalReserve, single: total=33.56MiB, used=0.00B

raps-debian btrfs # btrfs fi usage /mnt/btrfs/
Overall:
    Device size:                  32.00GiB
    Device allocated:             32.00GiB
    Device unallocated:            1.04MiB
    Device missing:                  0.00B
    Used:                         31.03GiB
    Free (estimated):            549.41MiB      (min: 549.41MiB)
    Data ratio:                       1.00
    Metadata ratio:                   2.00
    Global reserve:               33.56MiB      (used: 0.00B)

Data,single: Size:31.50GiB, Used:30.96GiB
   /dev/vdb1      31.50GiB

Metadata,DUP: Size:222.94MiB, Used:33.69MiB
   /dev/vdb1     445.88MiB

System,DUP: Size:32.00MiB, Used:16.00KiB
   /dev/vdb1      64.00MiB

Unallocated:
   /dev/vdb1       1.04MiB
raps-debian btrfs #



hm ... hasn't worked.
wrong tool ? did i missed something
or have i completely misunderstood deduplication?


Greetings
Markus