File Systems

If you ask this question, probably the one which is default for your distribution or ext4.

Some good file systems and their usage:

Could be that you ran out of inodes. Check with df -i.

SSDs do garbage collection differently, which is why dd if=/dev/true or scrub don't work properly.

• xfs scrub can TRIM the SSD's free space
• you can use a systemd timer (fstrim.service / fstrim.timer) to TRIM periodically
• you can enable the discard mount option to TRIM immediately after deleting a file, which slows down deleting files a fair bit.

lazy inode init makes the drive behave slowly on first mount

mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/sdXY

Huge amount = >300k

mount with dir_index

if the error EXT4-fs warning (device /dev/sdx): ext4_dx_add_entry: Directory index full! occurs, you probably have more than 2 million files in one directory, check with

$ cd /var/
$ debugfs
debugfs> open /dev/sdd1
debugfs> cd log/
debugfs> htree .
[...]
Number of Entries (count): 508
Number of Entries (limit): 508
[...]

and remedy with fsck.ext4 -yfD /dev/sdx1

(source)

For interoperability with Windows; is mounted with FUSE and therefore pretty slow.

Use mount options fmask=117,dmask=007 so the executable bit isn't set on everything.

• exFAT vs NTFS on Linux

• Can and should UDF be used as a hard drive format?
• Format UDF