Right way to check free/used storage of btrfs filesystem [SOLVED]
Right way to check free/used storage of btrfs filesystem [SOLVED]
While checking for used and free space in a btrfs subvolume, I'm not getting a consistent value. It's confusing and doesn't help.
- What is the correct way to find used/free space?
- Why are these values inconsistent (except normal du)?
According to btrfs fi usage /home, 83.21 GiB is used.
Overall:
Device size: 149.98GiB
Device allocated: 100.07GiB
Device unallocated: 49.91GiB
Device missing: 0.00B
Device slack: 0.00B
Used: 83.21GiB
Free (estimated): 63.06GiB (min: 38.10GiB)
Free (statfs, df): 63.06GiB
Data ratio: 1.00
Metadata ratio: 2.00
...
As per btrfs fi df /home, used space is 82.86 GiB, not 83.21 GiB.
Data, single: total=96.01GiB, used=82.86GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=2.00GiB, used=178.61MiB
GlobalReserve, single: total=99.50MiB, used=0.00B
As per btrfs fi du -s /home , used space is 63.11 GiB.
Total Exclusive Set shared Filename
63.11GiB 13.64GiB 49.01GiB /home
While according to du -hs /home, 64GiB is used.
Also, maximum space used should be close to 72 GiB as per btrfs fi du -s / and 73 GiB as per du -hs /, if btrfs fi usage includes all subvolumes . '/home' and '/' are on separate subvolumes.
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As per
btrfs fi df /home, used space is 82.86 GiB, not 83.21 GiB.That's just used data. The global used metric likely incorporates metadata etc. too. System aswell as the GlobalReserve are probably accounted as fully used as they're, well, reserved.
As per
btrfs fi du -s /home, used space is 63.11 GiB.Total Exclusive Set shared Filename 63.11GiB 13.64GiB 49.01GiB /homeWhile according to
du -hs /home, 64GiB is used.Likely compression or inline extents. btrfs only reports apparent size to
duand friends unfortunately.Also, maximum space used should be close to 72 GiB as per
btrfs fi du -s /and 73 GiB as perdu -hs /, ifbtrfs fi usageincludes all subvolumes . '/home' and '/' are on separate subvolumes.Your home has a lot of shared extents which indicates to me that you have at least one snapshot of it.
You also wrote 13.6GiB of new data to your home since the snapshot. Assuming a similar amount of data was deleted/overwritten since, that would add up to 76GiB. If there's perhaps one or two more snapshots, that would explain the rest.
Snapshots are "free" only so long as you don't write or delete any data in the origin.
Thanks that helped. I have one snapshot of home.
Size of diff between btrfs subvolume andAdditional space used by snapshot is 11GiB (probably) andbtrfs fi du -s /is 72GiB, making 83GiB (closer tobtrfs fi df /).Size of diff between btrfs subvolume and snapshot is 11GiB
WDYM by "diff"?
Also forgot to mention but if you want to know what's taking how much space on your btrfs, try
btdu. It uses a sampling-based approach and will therefore never be 100% accurate but it should be quite accurate enough after a little bit.just comparing the subvolume with its snapshot with
btrfs send -p /example/subvol /snapshot/of/example/subvol >examplediff.btrfs.From
man btrfs-sendgenerate a stream of instructions that describe changes between two subvolume snapshots
Thanks for btdu, it seems useful as 'btrfs fi du' probably doesn't account for compression, will check it out sometime.
Note that the diff does not necessarily correlate with the amount of data that changed, not how much additional space the snapshot takes.
You are right. I shouldn't have used diff. I'll fix that
Also, incremental changes from subvolume to its snapshot might be incorrect as that will be new data added to subvolume, rather that old data deleted from subvolume while still present in snapshot. I'll have to check carefully.