The metadata sub-system is responsible to store all information regarding the Filesystem and its files.

For accomplish this goal it relies on the following components: Fstab, Filesystem, NameSystem and MetadataServer.

Fstab

Contains information about all FS on the system. It stores the following data:

• fsentry: fs_id, local folder path, remote folder path

Metadata file

• filesystems - contains control block for all fs

Filesystem

Contains all the file metadata for a given FS. It stores the following data:

• index: file_id, relative path, inode position
• inode: size, checksum, modificationTS, status

Metadata files

• .control - inode table
• .inodes - contains the inode entries, one per line - fixed size

NamingServer

Resolve identifier to resources. This is the only component of the metadata sub-system that is exposed by the kernel facade.

Identifier format

nsync:[:file_id]

Operations

• given a fs_id and relative path, returns an Identifier
• given a identifier, returns a resource

Resources

• FSMeta: uri, local path, remote path
• FileInfo: uri, relative path, size, checksum, modificationTS, status

MetadataServer

The metadata server is responsible by manipulating the metadata structures (fstab and filesystems) directly.