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=============
volume.config
=============

.. configfile:: volume.config

The :file:`volume.config` file enables you to manage your cache space more
efficiently and restrict disk usage by creating cache volumes of
different sizes for specific protocols. You can further configure these
volumes to store data from certain origin servers and/or domains in the
:file:`hosting.config` file.

.. important::

    The volume configuration must be the same on all nodes in
    a cluster. You must stop Traffic Server before you change the cache
    volume size and protocol assignment. For step-by-step instructions about
    partitioning the cache, refer to :ref:`partitioning-the-cache`.

Format
======

For each volume you want to create, enter a line with the following
format: ::

    volume=volume_number  scheme=protocol_type  size=volume_size

where ``volume_number`` is a number between 1 and 255 (the maximum
number of volumes is 255) and ``protocol_type`` is ``http``. Traffic
Server supports ``http`` for HTTP volume types; ``volume_size`` is the
amount of cache space allocated to the volume. This value can be either
a percentage of the total cache space or an absolute value. The absolute
value must be a multiple of 128 MB, where 128 MB is the smallest value.
If you specify a percentage, then the size is rounded down to the
closest multiple of 128 MB.

Each volume is striped across several disks to achieve parallel I/O. For
example: if there are four disks, then a 1-GB volume will have 256 MB on
each disk (assuming each disk has enough free space available). If you
do not allocate all the disk space in the cache, then the extra disk
space is not used. You can use the extra space later to create new
volumes without deleting and clearing the existing volumes.

Examples
========

The following example partitions the cache evenly between HTTP and HTTPS
requests::

    volume=1 scheme=http size=50%
    volume=2 scheme=http size=50%