How to use the command "compsize" (with examples)

The “compsize” command is used to calculate the compression ratio of a set of files on a btrfs filesystem. It can be useful for analyzing the efficiency of data compression and identifying files or directories that can be further optimized for space utilization. This article will illustrate three use cases of the “compsize” command with relevant examples.

Use case 1: Calculate the current compression ratio for a file or directory

Code:

sudo compsize path/to/file_or_directory

Motivation:

Calculating the compression ratio of a specific file or directory can provide insights into how effectively the data is being compressed. It can be helpful in identifying files that are taking up a significant amount of space on the filesystem and optimizing them for compression.

Explanation:

• sudo: The “sudo” command is used to run the “compsize” command with administrative privileges, as it may require access to certain system files and directories.
• compsize: The actual command that is being executed.
• path/to/file_or_directory: Specifies the path of the file or directory for which the compression ratio needs to be calculated.

Example output:

processed 1 file, zero size 196608 bytes, 135168 bytes compressed

In this example, the “compsize” command calculated the compression ratio for a specific file. It displays the number of bytes in the file before compression, the number of bytes that were actually stored on the filesystem, and the amount of compression achieved.

Use case 2: Don’t traverse filesystem boundaries

Code:

sudo compsize --one-file-system path/to/file_or_directory

Motivation:

By default, the “compsize” command traverses all filesystem boundaries and analyzes the compression ratio of files and directories across different filesystems. However, in certain scenarios, you may want to restrict the analysis to a specific filesystem to get a more accurate representation of the compression efficiency within that filesystem.

Explanation:

• --one-file-system: This option instructs the “compsize” command to only consider files and directories within the specified path, without traversing any filesystem boundaries.

Example output:

processed 1 file, zero size 32768 bytes, 23552 bytes compressed

The output for this example is similar to the previous one, but the “compsize” command only calculated the compression ratio within the specified filesystem and did not consider any files or directories outside of it.

Use case 3: Show raw byte counts instead of human-readable sizes

Code:

sudo compsize --bytes path/to/file_or_directory

Motivation:

The “compsize” command usually displays human-readable sizes, such as kilobytes or megabytes, for easier interpretation. However, in certain scenarios, you may need to obtain raw byte counts for more precise calculations or further processing.

Explanation:

• --bytes: This option instructs the “compsize” command to display the compression ratio in raw byte counts instead of human-readable sizes.

Example output:

processed 1 file, zero size 196608 bytes, 135168 bytes compressed

The output for this example is the same as the output in the first use case. However, the byte counts are displayed in their raw format, providing a more precise measurement of the compression efficiency.

Conclusion:

The “compsize” command is a useful tool for calculating the compression ratio of files and directories on a btrfs filesystem. By analyzing the compression efficiency, you can identify opportunities for optimizing storage space and improving overall data management. The three use cases illustrated in this article demonstrate different scenarios in which the “compsize” command can be applied to meet specific requirements.