.. _storage-migration:

Migrate Data to Another Disk
===========================================

High disk load may lead to delays in event arrivals. In severe cases, it might result in complete inoperability of FindFace Multi. One of the means for reducing the disk load is to migrate the FindFace Multi data storages to another disk.

.. rubric:: In this section:

.. contents::
   :local:

.. _prepare-disk:

Prepare Disk
--------------------

To prepare a disk for the data migration, do the following:

#. Create a new mount point (``/mnt/ffdata`` in our example).

   .. code::

      sudo mkdir /mnt/ffdata
      sudo chown ntech:ntech /mnt/ffdata

#. Create a partition.

   .. code::

      sudo parted /dev/sdb
      mklabel gpt
      mkpart primary ext4 1MiB 100%
      q
      sudo mkfs.ext4 /dev/sdb1

#. Learn the UUID of the partition (``sdb1`` in our example).

   .. code::

      sudo blkid | grep sdb1
      /dev/sdb1: LABEL="data" UUID="0638ebe0-853e-43ea-8f35-bfae305695d1" TYPE="ext4" PARTUUID="8cebaacc-77d7-4757-b4c6-14147e92646c"

#. Add the partition to fstab to make it automatically mount on booting. 

   .. code::

      sudo vi /etc/fstab 
      ------------
      #DATA mount
      UUID=0638ebe0-853e-43ea-8f35-bfae305695d1 /mnt/ffdata/    ext4    auto,user,rw     0       2
      -------------

#. Mount all the filesystems.

   .. code::

      sudo mount -a


Migrate Photo Storage
-----------------------------

To migrate the FindFace Multi photo storage, do the following:

#. Stop the ``findface-security`` service to prevent the data loss.

   .. code::

      sudo systemctl stop findface-security

#. By default, the photo data are stored at ``/var/lib/``. Migrate the photo storage to the :ref:`new disk <prepare-disk>`.

   .. code::
    
      sudo cp -ax /var/lib/findface-security/ -R /mnt/ffdata/
      sudo rm -r /var/lib/findface-security/
      sudo cp -ax /var/lib/ffupload/ -R /mnt/ffdata/
      sudo rm -r /var/lib/ffupload/

#. Create symbolic links for the new directories.

   .. code::

      sudo ln -s /mnt/ffdata/findface-security/ /var/lib/
      sudo ln -s /mnt/ffdata/ffupload/ /var/lib/

#. Ensure that the rights are correctly assigned.

   .. code::

      sudo chown ntech:ntech /mnt/ffdata/findface-security/

#. Start the ``findface-security`` service.

   .. code::

      sudo systemctl start findface-security


Migrate Main Database (PostgreSQL)
------------------------------------

To migrate the PostgreSQL database, do the following:

#. Learn the current database directory.

   .. code::

      postgres=# SHOW data_directory;
 
              data_directory
      ------------------------------
       /var/lib/postgresql/10/main

#. Stop PostgreSQL.

   .. code::

      sudo systemctl stop postgresql

#. Create a new directory that will hold the database and assign it to the ntech user.

   .. code::

      mkdir postgres_data_dir
      chown ntech postgres_data_dir

#. Migrate the database and backup the old one.

   .. code::

      sudo rsync -av /var/lib/postgresql /test/postgres_data_dir/
      sudo mv /var/lib/postgresql/10/main /backups/pg_backup

#. Substitute the directory in the PostgreSQL configuration file ``<PostgreSQL directory>/postgresql.conf``.

   .. code::

      data_directory = '/test/postgres_data_dir/postgresql/10/main' 

#. Start PostgreSQL. 

   .. code::

      sudo systemctl start postgresql

#. Check if the directory has successfully been changed.

   .. code::

      postgres=# SHOW data_directory; 
 
              data_directory
      --------------------------------------------
      /test/postgres_data_dir/postgresql/10/main