I have a 1G HDD which is used in LUKSv2 + LVM setup (10 logical disks). One of
the LVM disks is 320G in size. I had to split this partition into two smaller
ones of about 160G each. The partition was filled with 75G of data, so over 50%
was free.
To shrinked the partition using the following command:
# lvreduce -L -160G -r /dev/mapper/wd_blue_label-android
and after about 1 hour, the process was completed. When it was done, I initiated
e4defrag, to defrag the files, and I noticed, that even very small files
(10-100K in size) have 2+ extents:
[591612/591617]/media/Android/AIO-TWRP-Compiler/compile.log: 100% extents: 2 -> 2 [ OK ]
# ls -alh /media/Android/AIO-TWRP-Compiler/compile.log
-rw-r--r-- 1 morfik morfik 34K 2019-02-12 18:22:48 /media/Android/AIO-TWRP-Compiler/compile.log
# filefrag -ve /media/Android/AIO-TWRP-Compiler/compile.log
Filesystem type is: ef53
File size of /media/Android/AIO-TWRP-Compiler/compile.log is 33999 (9 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 7: 10684.. 10691: 8:
1: 8.. 8: 10692.. 10692: 1: last,eof
/media/Android/AIO-TWRP-Compiler/compile.log: 1 extent found
And there are many files like this one.
When the defragmentation process finished it's job, there was this summary at
the end:
Success: [ 510319/591617 ]
Failure: [ 81298/591617 ]
Total extents: 593408->593437
Fragmented percentage: 15%->15%
Fsck says something like this:
# fsck.ext4 -Dvf /dev/mapper/wd_blue_label-android
e2fsck 1.45.6 (20-Mar-2020)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 3A: Optimizing directories
Pass 4: Checking reference counts
Pass 5: Checking group summary information
android: ***** FILE SYSTEM WAS MODIFIED *****
591626 inodes used (5.64%, out of 10485760)
1311 non-contiguous files (0.2%)
265 non-contiguous directories (0.0%)
# of inodes with ind/dind/tind blocks: 0/0/0
Extent depth histogram: 587843/69
20222806 blocks used (48.21%, out of 41943040)
0 bad blocks
3 large files
516113 regular files
69686 directories
0 character device files
0 block device files
0 fifos
0 links
5818 symbolic links (3706 fast symbolic links)
0 sockets
------------
591617 files
and the free space looks like this:
# e2freefrag /dev/mapper/wd_blue_label-android
Device: /dev/mapper/wd_blue_label-android
Blocksize: 4096 bytes
Total blocks: 41943040
Free blocks: 21720234 (51.8%)
Min. free extent: 4 KB
Max. free extent: 2064256 KB
Avg. free extent: 8972 KB
Num. free extent: 9681
HISTOGRAM OF FREE EXTENT SIZES:
Extent Size Range : Free extents Free Blocks Percent
4K... 8K- : 306 306 0.00%
8K... 16K- : 432 997 0.00%
16K... 32K- : 1127 5672 0.03%
32K... 64K- : 3587 42393 0.20%
64K... 128K- : 1306 30025 0.14%
128K... 256K- : 837 37784 0.17%
256K... 512K- : 411 36730 0.17%
512K... 1024K- : 270 48248 0.22%
1M... 2M- : 243 86984 0.40%
2M... 4M- : 227 164786 0.76%
4M... 8M- : 239 343081 1.58%
8M... 16M- : 196 548225 2.52%
16M... 32M- : 149 833919 3.84%
32M... 64M- : 126 1389825 6.40%
64M... 128M- : 95 2199517 10.13%
128M... 256M- : 49 2322803 10.69%
256M... 512M- : 38 3497585 16.10%
512M... 1024M- : 31 5627846 25.91%
1G... 2G- : 12 4503508 20.73%
So how to read the data? Are the files in this partition really fragmented or
not?
--
Debian Sid
Linux version 5.8.0-amd64 (morfik@morfikownia) (gcc (Debian 10.2.0-3) 10.2.0, GNU ld (GNU Binutils for Debian) 2.35) #1 SMP PREEMPT Wed Aug 5 15:35:00 CEST 2020
e4defrag 1.45.6 (20-Mar-2020)