Which three are features of the btrfs file system?

The B-tree file system (btrfs) is a modern, copy-on-write (CoW) file system for Linux. Its core design includes several advanced features. It has integrated volume management, which allows it to manage multiple block devices, supporting various RAID levels, including mirroring (RAID1). As a fundamental characteristic, it uses a copy-on-write technique for both data and metadata, which enables robust features like snapshots and data integrity checks. Btrfs also supports online operations, including the ability to add or remove devices and resize the file system while it is mounted and in active use.

C. Cluster file system: Btrfs is not a cluster file system; it is designed for single-node use. Oracle Linux provides OCFS2 for clustered environments.

D. Efficient storage for small files: While btrfs can inline small files into its metadata structure, making storage efficient, options A, B, and E represent more primary, defining features listed in official documentation.

F. General-purpose volume manager: Btrfs has integrated volume management, but it is not a general-purpose, block-level volume manager like LVM, which is file-system-agnostic.

G. Automatic defragmentation: Defragmentation in btrfs is an online but manually initiated process or enabled via a non-default mount option (autodefrag); it is not an inherent, automatic background feature.

1. Oracle® Linux 8: Managing Local File Systems

Chapter 3

"About Btrfs". The documentation explicitly lists these key features:

"Copy-on-write (CoW) for both data and metadata" (Supports B)

"Integrated volume management

support for RAID 0

RAID 1

RAID 5

RAID 6

and RAID 10" (Supports A)

"Online volume growth and shrinking" (Supports E)

The document also clarifies

"Btrfs is not a clustered file system." (Refutes C)

2. Oracle® Linux 7: Administrator's Guide

Chapter 11

"The Btrfs File System". This guide states:

"Btrfs is a copy-on-write (CoW) file system..." (Supports B)

"You can add and remove devices from a mounted file system." (Supports E)

"Btrfs provides built-in RAID support

including mirroring (RAID1)..." (Supports A)

It describes defragmentation as a manual command: btrfs filesystem defragment. (Refutes G)