nbdserver

NBD Server for blocks stored in ARDB

NBD Server Configuration

The NBD server and its backend is configured using a YAML configuration file:

storageClusters: # A required map of storage clusters,
                 # only 1 storage cluster is required
  mycluster: # Required (string) ID of this storage cluster,
             # you are free to name the cluster however you want
    dataStorage: # A required array of connection (dial)strings, used to store data
      - address: 192.168.58.146:2000 # At least 1 connection (dial)string is required
        db: 0                        # database is optional, 0 by default
      - address: 192.123.123.123:2001 # more connections are optional
    metadataStorage: # Required ONLY when used as the (Root)StorageCluster of a `boot` vdisk
      address: 192.168.58.146:2001 # Required connection (dial)string,
                                   # used to store meta data (LBA indices)
  rootcluster: # Required (string) ID of this (optional) storage cluster,
               # you are free to name the cluster however you want
    dataStorage: # A required array of connection (dial)strings, used to store data
      - address: 192.168.58.147:2000 # only 1 connection (dial)string is required
        db: 1                        # database is optional, 0 by default
    metadataStorage: # Required ONLY when used as the (Root)StorageCluster of a `boot` vdisk
      address: 192.168.58.147:2001 # Required connection (dial)string
  # ... more (optional) storage clusters
vdisks: # A required map of vdisks,
        # only 1 vdisk is required,
        # the ID of the vdisk is the same one that the user of this vdisk (nbd client)
        # used to connect to this nbdserver
  myvdisk: # Required (string) ID of this vdisk
    blockSize: 4096 # Required static (uint64) size of each block
    readOnly: false # Defines if this vdisk can be written to or not
                    # (optional, false by default)
    size: 10 # Required (uint64) total size in GiB of this vdisk
    storageCluster: mycluster # Required (string) ID of the storage cluster to use
                              # for this vdisk's storage, has to be a storage cluster
                              # defined in the `storageClusters` section of THIS config file

    slaveStorageCluster: slaveCluster # Optional (string) ID of the storage cluster to use
                                      # for this vdisk's storage, has to be a storage cluster
                                      # defined in the `storageClusters` section of THIS config file
    rootStorageCluster: rootcluster # Optional (string) ID of the (root) storage cluster to use
                                    # for this vdisk's fallback/root/template storage, has to be
                                    # a storage cluster defined in the `storageClusters` section
                                    # of THIS config file
    rootVdiskID: mytemplate # Optional (string) ID of the template vdisk,
                            # only used for `db` vdisks
    type: boot # Required (VdiskType) type of this vdisk
               # which also defines if its deduped or nondeduped,
               # valid types are: `boot`, `db`, `cache` and `tmp`
  # ... more (optional) vdisks

As you can see, both the storage clusters and vdisks are configured in and within the same NBD server config.yml file.

By default the nbdserver executable assumes the config.yml file exists within the working directory of its process. This location can be defined using the --config path optional CLI flag.

Live reloading of the configuration

A running nbdserver in a production environment can not simply be restarted since this will break the connection to any connected client. When the configuration file is modified, send a SIGHUP signal to the nbdserver to make it pick up the changes.

NOTE: It is not recommended to change the configs of storage clusters, whichare still in use by active (connected) clients, and content might get lost if you do this anyway.

Usage

Use nbdserver -h or nbdserver --help to get more information about all available flags.

Example

Make sure you have an ARDB server(s) running, on the connection info specified in the used config.yml file.

make nbdserver && bin/nbdserver -protocol tcp -address ":6666"

You can also instead simply run the nbdserver with no flag specified bin/nbdserver to run it on the default /tmp/nbd-socket unix socket, which is the same as the more explicit version bin/nbdserver -protocol unix --address /tmp/nbd-socket.

Note that if you don't have the config.yml file in your current working directory, you'll have to specify the config file explicitly using the -config path flag.

Connect your nbd-client to the server running on localhost:6666:

sudo nbd-client -b 4096 -name default localhost 6666 /dev/nbd1
sudo mkfs.ext4 -b 4096 /dev/nbd1
sudo mount /dev/nbd1 /mnt/sharedvolume

Converting an image using 'qemu-img' to insert an image in the NBD server:

apt-get install qemu-utils

When the NBD server is running on a TCP socket:

qemu-img convert -p -n ubuntu-16.04-server-cloudimg-amd64-disk1.img -O nbd nbd+tcp://[HOST]:[PORT]/[VDISKID]

When the NBD server is running on a Unix socket:

qemu-img convert -p -n ubuntu-16.04-server-cloudimg-amd64-disk1.img -q nbd nbd+unix:///[VDISKID]?socket=/tmp/nbd-socket

More

For more verbose documentation see the /docs directory.

You'll find there following sections about the NBD Server:

• NBD Server Introduction
• Building your NBD Server
• NBD Server Configuration
• Using your NBD Server

For more information about the internals of the NBD Server you can find the following sections:

• The types of Backend Storage and how they work
• The LBA Lookups of the Deduped Backend Storage