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CosmOS Virtual File System

CosmOS has a hierarchical file system, similar to POSIX. A VFS node is defined as:

struct vfs {
    enum vfs_type type;
    struct arraylist* children;

    /*
    This is a filename or a folder name
    For a device, or a fs, it's the dev name, since a fs is a dev
    */
    uint8_t* name;

    vfs_open_function open;
    vfs_read_function read;
    vfs_write_function write;
    vfs_close_function close;
    vfs_close_readdir_function readdir;
};

CosmoS VFS nodes can be files, folders, or devices. CosmOS OS uses devices for file systems, and therefore does not need mount points represented in vfs's.

Design

CosmOS VFS (Virtual File System)

A core design goal of CosmOS is that it exposes a single root file system that includes all devices and filesystems on all nodes

VFS Hierarchy

The basic hierarchy seen by every node is

	<node_name>/<filesystem_name>

and

	<node_name>/dev/<device_name>

For example presuming we have two nodes "bart" and "lisa"

/
/bart/fat0
/bart/dev/serial0
/lisa/fat0
/lisa/fat1
/lisa/dev/serial0
/lisa/dev/serial1

Sync

The CosmOS cluster will sync the VFS implementations on each node as nodes come online and go offline, and as devices are attached and detached

Nodes

CosmOS will expose a node filesystem which contains information for each node in the system such as

  • Uptime
  • Total RAM in the system
  • Total RAM in use
  • Total Processors in the system
  • Processor Usage
  • Network throughput

This information will be useful for process migrations.

For example

/node/bart
/node/lisa

Processes

In theory, CosmOS can also expose a process filesystem, similar to the dev filesystem which contains every process on every node. For example

/bart/process/process_abc
/bart/process/process_def