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# Configuring Memory Caching

You can significantly improve your Nextcloud 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 Nextcloud admin page. A memcache is not required and you may safely 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 for PHP 5.5+.

If you are using PHP 5.4, which is the oldest supported PHP version for Nextcloud, 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.

Nextcloud 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 4.0.6 and up required.

    A local cache for systems running PHP 5.5 and up.

- Memcached

    Distributed cache for multi-server Nextcloud installations.

- Redis, PHP module 2.2.5 and up required.

    For distributed caching.

Memcaches must be explicitly configured in Nextcloud 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 PHP Version and Information.

## APC

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

Note

RHEL 6 and CentOS 6 ship with PHP 5.3 and must be upgraded to PHP 5.4 to run Nextcloud. 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 Nextcloud admin page, and the cache warning should disappear.

## APCu

PHP 5.5 and up include 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`. On Ubuntu 14.04LTS, the APCu version is 4.0.2, which is too old to use with Nextcloud. Nextcloud requires 4.0.6+. You may install 4.0.7 from Ubuntu backports with this command:

    apt-get install php5-apcu/trusty-backports

Then restart your Web server.

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

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

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

## Memcached

Memcached is a reliable oldtimer for shared caching on distributed servers, and performs well with Nextcloud with one exception: it is not suitable to use with Transactional File Locking because it does not store locks, and data can disappear from the cache at any time (Redis is the best memcache for this).

Note

Be sure to install the memcached PHP module, and not memcache, as in the following examples. Nextcloud 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 Nextcloud 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 for Transactional File Locking 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+. If you are running a Linux distribution that does not package the supported versions of this module, or does not package Redis at all, see Additional Redis Installation Help.

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 CentOS and 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 Nextcloud 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,
          ),

For best performance, use Redis for file locking by adding this:

    'memcache.locking' => '\OC\Memcache\Redis',

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

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

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

## 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.

## Recommendations Based on Type of Deployment

### Small/Private Home Server

Only use APCu:

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

### Small Organization, Single-server Setup

Use APCu for local caching, Redis for file locking:

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

### Large Organization, Clustered Setup

Use Redis for everything except local memcache:

    'memcache.distributed' => '\OC\Memcache\Redis',
    'memcache.locking' => '\OC\Memcache\Redis',
    'memcache.local' => '\OC\Memcache\APCu',
    'redis' => array(
         'host' => 'localhost',
         'port' => 6379,
          ),

### Additional notes for Redis vs. APCu on Memory Caching

APCu is faster at local caching than Redis. If you have enough memory, use APCu for Memory Caching and Redis for File Locking. If you are low on memory, use Redis for both.

## Additional Redis Installation Help

If your version of Mint or Ubuntu does not package the required version of `php5-redis`, then try this Redis guide on Tech and Me for a complete Redis installation on Ubuntu 14.04 using PECL. These instructions are adaptable for any distro that does not package the supported version, or that does not package Redis at all, such as SUSE Linux Enterprise Server and Red Hat Enterprise Linux.

The Redis PHP module must be at least version 2.2.5. Please note that the Redis PHP module versions 2.2.5 - 2.2.7 will only work for:

    PHP version 6.0.0 or older
    PHP version 5.2.0 or newer

See https://pecl.php.net/package/redis

On Debian/Mint/Ubuntu, use `apt-cache` to see the available `php5-redis` version, or the version of your installed package:

    apt-cache policy php5-redis

On CentOS and Fedora, the `yum` command shows available and installed version information:

    yum search php-pecl-redis

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