There are a lot of 4T hard drives remaining, prompting "No space left on device" insufficient disk space

In linux, there are two concepts of hard disk, namely block and inode

• block: used to store actual data, the actual occupied space can be viewed with df -h
• inode: store file attributes, the actual occupied node is viewed with df -i

As long as one of these two is full, it will cause the error "No space left on device" to be prompted for insufficient disk space, that is, if all inodes in the file system are exhausted, even if there is free space on the disk,The kernel also cannot create new files.

After formatting the disk with the default parameters of mkfs.ext4, it is found that the formatting time is very long, and the formatting takes up a lot of space on the disk.For example, it will take about 10 minutes to format a 2TB disk and occupy about 30G of disk space.
The reason is that the original inode will occupy disk space, and each inode occupies 256b of space.
By default, mkfs2fs allocates an inode for every 16kb of disk space;

So, when creating a new filesystem on a partition, you can use the -i option to set the bytes per inode (bytes/inode ratio), the larger the bytes per inode ratio, the fewer inodes will be created.For example:

$ sudo mkfs.ext4 -i 16400 /dev/sdc1

Note: Once a filesystem is created, the bytes-per-inode ratio cannot be changed (unless reformatted), whereas resizing a filesystem changes the number of inodes to maintain that ratio.

Linux Quick Format Command

Use the -T flag to specify how the filesystem will be used, telling the filesystem will be used to create or store largefile and largefile4, which provide more ratios, i.e. one inode per 1 MiB and 4 MiB, respectively, reducing the number of inodes,The formatting rate will also be faster.

$ sudo mkfs.ext4 -T largefile /dev/device
$ sudo mkfs.ext4 -T largefile4 /dev/device

[How much disk space to allocate an inode] corresponding to largefile and largefile4 is actually defined in /etc/mke2fs.conf.
largefile type is 1M one inode
largefile4 type is 4M one inode

This format will be faster, but the inode will be reduced. If you are sure that all large files are stored, it can be used in this way. If all small files are stored, there will be a lot of remaining space on the disk when inodes are exhausted, butPrompt "No space left on device" when the disk space is insufficient to create a file: