Storage Elements in AEM 6.5 storage-elements-in-aem
This article covers the following:
Overview of Storage in AEM 6 overview-of-storage-in-aem
One of the most important changes in AEM 6 are the innovations at the repository level.
Currently, there are two node storage implementations available in AEM6: Tar storage, and MongoDB storage.
Tar Storage tar-storage
Running a freshly installed AEM instance with Tar Storage running-a-freshly-installed-aem-instance-with-tar-storage
By default, AEM 6 uses the Tar storage to store nodes and binaries, using the default configuration options. You can manually configure its storage settings by doing the following:
-
Download the AEM 6 quickstart jar and place it in a new folder.
-
Unpack AEM by running:
java -jar cq-quickstart-6.jar -unpack
-
Create a folder named
crx-quickstart\install
in the installation directory. -
Create a file called
org.apache.jackrabbit.oak.segment.SegmentNodeStoreService.cfg
in the newly created folder. -
Edit the file and set the configuration options. The following options are available for Segment Node Store, which is the basis of AEM’s Tar storage implementation:
repository.home
: Path to repository home under which various repository-related data is stored. By default segment files would be stored under the crx-quickstart/segmentstore directory.tarmk.size
: Maximum size of a segment in MB. The default is 256 MB.
-
Start AEM.
Mongo Storage mongo-storage
Running a freshly installed AEM instance with Mongo Storage running-a-freshly-installed-aem-instance-with-mongo-storage
AEM 6 can be configured to run with MongoDB storage by following the below procedure:
-
Download the AEM 6 quickstart jar and place it into a new folder.
-
Unpack AEM by running the following command:
java -jar cq-quickstart-6.jar -unpack
-
Make sure that MongoDB is installed and an instance of
mongod
is running. For more info, see Installing MongoDB. -
Create a folder named
crx-quickstart\install
in the installation directory. -
Configure the node store by creating a configuration file with the name of the configuration that you want to use in the
crx-quickstart\install
directory.The Document Node Store (which is the basis for AEM’s MongoDB storage implementation) uses a file called
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService.cfg
-
Edit the file and set your configuration options. The following options are available:
mongouri
: The MongoURI required to connect to Mongo Database. The default ismongodb://localhost:27017
db
: Name of the Mongo database. By default new AEM 6 installations use aem-author as the database name.cache
: The cache size in megabytes. This cache size is distributed among various caches used in DocumentNodeStore. The default is 256.changesSize
: Size in MB of capped collection used in Mongo for caching the diff output. The default is 256.customBlobStore
: Boolean value indicating that a custom data store is used. The default is false.
-
Create a configuration file with the PID of the data store you want to use and edit the file to set the configuration options. For more info, see Configuring Node Stores and Data Stores.
-
Start the AEM 6 jar with a MongoDB storage backend by running:
code language-shell java -jar cq-quickstart-6.jar -r crx3,crx3mongo
Where the backend run mode is
-r
, the example starts with MongoDB support.
Disabling Transparent Huge Pages disabling-transparent-huge-pages
Red Hat® Linux® uses a memory management algorithm called Transparent Huge Pages (THP). While AEM performs fine-grained reads and writes, THP is optimized for large operations. Therefore, it is recommended that you disable THP both on Tar and Mongo storage. To disable the algorithm, follow these steps:
-
Open the
/etc/grub.conf
file in the text editor of your choice. -
Add the following line to the grub.conf file:
code language-none transparent_hugepage=never
-
Finally, check if the setting has taken effect by running:
code language-none cat /sys/kernel/mm/redhat_transparent_hugepage/enabled
If THP is disabled, the output of the above command should be:
code language-none always madvise [never]
Maintaining the Repository maintaining-the-repository
Each update to the repository creates a content revision. As a result, with each update the size of the repository grows. To avoid uncontrolled repository growth, old revisions must be cleaned up to free disk resources. This maintenance functionality is called Revision Cleanup. The Revision Cleanup mechanism reclaims disk space by removing obsolete data from the repository. For further details about Revision Cleanup, read the Revision Cleanup page.