# ownCloud 8.0 Server Administration Manual

# Configuring Memory Caching

You can significantly improve your ownCloud server performance with memory caching, where frequently-requested objects are stored in memory for faster retrieval. There are two types of caches to use: a PHP opcode cache, which is commonly called opcache, and data caching for your Web server. If you do not install and enable a local memcache you will see a warning on your ownCloud admin page. A memcache is not required and you may ignore the warning if you prefer.

Note

If you enable only a distributed cache in your `config.php` (`memcache.distributed`) and not a local cache (`memcache.local`) you will still see the cache warning.

A PHP opcache stores compiled PHP scripts so they don’t need to be re-compiled every time they are called. PHP bundles the Zend OPcache in core since version 5.5, so you don’t need to install an opcache.

If you are using PHP 5.4, which is the oldest supported PHP version for ownCloud, you may install the Alternative PHP Cache (APC). This is both an opcache and data cache. APC has not been updated since 2012 and is essentially dead, and PHP 5.4 is old and lags behind later releases. If it is possible to upgrade to a later PHP release that is the best option.

Data caching is supplied by the Alternative PHP Cache, user (APCu) in PHP 5.5+, Memcached, or Redis.

ownCloud supports multiple memory caching backends, so you can choose the type of memcache that best fits your needs. The supported caching backends are:

- APC

    A local cache for systems running PHP 5.4.

- APCu, APCu 4.06 and up required.

    A local cache for systems running PHP 5.5 and up.

- Memcached

    Distributed cache for multi-server ownCloud installations.

- Redis, PHP module 2.2.5 and up required.

    For distributed caching, and required for Transactional File Locking.

These are supported but not recommended:

- XCache
- ArrayCache

Memcaches must be explicitly configured in ownCloud 8.1 and up by installing and enabling your desired cache, and then adding the appropriate entry to `config.php` (See Config.php Parameters for an overview of all possible config parameters).

You may use both a local and a distributed cache. Recommended caches are APCu and Redis. After installing and enabling your chosen memcache, verify that it is active by running phpinfo.

## APC

APC is only for systems running PHP 5.4 and older. The oldest supported PHP version in ownCloud is 5.4.

Note

RHEL 6 and CentOS 6 ship with PHP 5.3 and must be upgraded to PHP 5.4 to run ownCloud. See Installing PHP 5.4 on RHEL 6 and CentOS 6.

On Red Hat/CentOS/Fedora systems running PHP 5.4, install `php-pecl-apc`. On Debian/Ubuntu/Mint systems install `php-apc`. Then restart your Web server.

After restarting your Web server, add this line to your `config.php` file:

    'memcache.local' => '\OC\Memcache\APC',

Refresh your ownCloud admin page, and the cache warning should disappear.

## APCu

PHP 5.5 and up includes the Zend OPcache in core, and on most Linux distributions it is enabled by default. However, it does not bundle a data cache. APCu is a data cache, and it is available in most Linux distributions. On Red Hat/CentOS/Fedora systems running PHP 5.5 and up install `php-pecl-apcu`. On Debian/Ubuntu/Mint systems install `php5-apcu`. Then restart your Web server.

The version of APCu must be 4.0.6 and up.

After restarting your Web server, add this line to your `config.php` file:

    'memcache.local' => '\OC\Memcache\APCu',

Refresh your ownCloud admin page, and the cache warning should disappear.

## Memcached

Memcached is a reliable oldtimer for shared caching on distributed servers, and performs well with ownCloud.

Note

Be sure to install the memcached PHP module, and not memcache, as in the following examples. ownCloud supports only the memcached PHP module.

Setting up Memcached is easy. On Debian/Ubuntu/Mint install `memcached` and `php5-memcached`. The installer will automatically start `memcached` and configure it to launch at startup.

On Red Hat/CentOS/Fedora install `memcached` and `php-pecl-memcached`. It will not start automatically, so you must use your service manager to start `memcached`, and to launch it at boot as a daemon.

You can verify that the Memcached daemon is running with `ps ax`:

    ps ax | grep memcached
    19563 ? Sl 0:02 /usr/bin/memcached -m 64 -p 11211 -u memcache -l
    127.0.0.1

Restart your Web server, add the appropriate entries to your `config.php`, and refresh your ownCloud admin page. This example uses APCu for the local cache, Memcached as the distributed memcache, and lists all the servers in the shared cache pool with their port numbers:

    'memcache.local' => '\OC\Memcache\APCu',
    'memcache.distributed' => '\OC\Memcache\Memcached',
    'memcached_servers' => array(
         array('localhost', 11211),
         array('server1.example.com', 11211),
         array('server2.example.com', 11211),
         ),

## Redis

Redis is an excellent modern memcache to use for both distributed caching, and as a local cache because it guarantees that cached objects are available for as long as they are needed.

The Redis PHP module must be version 2.2.5 and up.

On Debian/Ubuntu/Mint install `redis-server` and `php5-redis`. The installer will automatically launch `redis-server` and configure it to launch at startup.

On Red Hat/CentOS/Fedora install `redis` and `php-pecl-redis`. It will not start automatically, so you must use your service manager to start `redis`, and to launch it at boot as a daemon.

You can verify that the Redis daemon is running with `ps ax`:

    ps ax | grep redis
    22203 ? Ssl    0:00 /usr/bin/redis-server 127.0.0.1:6379

Restart your Web server, add the appropriate entries to your `config.php`, and refresh your ownCloud admin page. This example `config.php` configuration uses Redis for the local server cache:

    'memcache.local' => '\OC\Memcache\Redis',
    'redis' => array(
         'host' => 'localhost',
         'port' => 6379,
         'timeout' => 0.0,
          ),

If you want to connect to Redis configured to listen on a Unix socket (which is recommended if Redis is running on the same system as ownCloud) use this example `config.php` configuration:

    'memcache.local' => '\OC\Memcache\Redis',
    'redis' => array(
         'host' => '/var/run/redis/redis.sock',
         'port' => 0,
         'timeout' => 0.0,
          ),

Redis is very configurable; consult the Redis documentation to learn more.

If you are on Ubuntu you can follow this guide for a complete installation from scratch.

## Cache Directory Location

The cache directory defaults to `data/$user/cache` where `$user` is the current user. You may use the `'cache_path'` directive in `config.php` (See Config.php Parameters) to select a different location.