Send/receive 发送/接收 

Send and receive are complementary features that allow to transfer data from one filesystem to another in a streamable format. The send part traverses a given read-only subvolume and either creates a full stream representation of its data and metadata (full mode), or given a set of subvolumes for reference it generates a difference relative to that set (incremental mode).
发送和接收是互补功能，允许以可流式传输的格式将数据从一个文件系统传输到另一个文件系统。发送部分遍历给定的只读子卷，并创建其数据和元数据的完整流表示（完整模式），或者根据一组用于参考的子卷生成相对于该集合的差异（增量模式）。

Receive on the other hand takes the stream and reconstructs a subvolume with files and directories equivalent to the filesystem that was used to produce the stream. The result is not exactly 1:1, e.g. inode numbers can be different and other unique identifiers can be different (like the subvolume UUIDs). The full mode starts with an empty subvolume, creates all the files and then turns the subvolume to read-only. At this point it could be used as a starting point for a future incremental send stream, provided it would be generated from the same source subvolume on the other filesystem.
接收端接收流并重建一个子卷，其中包含与用于生成流的文件系统等效的文件和目录。结果并非完全一对一，例如 inode 编号可能不同，其他唯一标识符也可能不同（如子卷 UUID）。完整模式从空子卷开始，创建所有文件，然后将子卷变为只读。此时，它可以用作将来增量发送流的起点，前提是它是从另一个文件系统上的相同源子卷生成的。

The stream is a sequence of encoded commands that change e.g. file metadata (owner, permissions, extended attributes), data extents (create, clone, truncate), whole file operations (rename, delete). The stream can be sent over network, piped directly to the receive command or saved to a file. Each command in the stream is protected by a CRC32C checksum. See btrfs-send(8) and btrfs-receive(8) for more.
该流是一系列编码命令，用于更改文件元数据（所有者、权限、扩展属性）、数据范围（创建、克隆、截断）、整个文件操作（重命名、删除）等。流可以通过网络发送，直接传输到接收命令或保存到文件中。流中的每个命令都受 CRC32C 校验和保护。有关更多信息，请参阅 btrfs-send(8)和 btrfs-receive(8)。