There is a tutorial how to set up Liferay to use Amazon Simple Storage Service in official user guide for Liferay Portal 6.1 ( http://www.liferay.com/documentation/liferay-portal/6.1/user-guide/-/ai/liferay-clusteri-2 ).
Unfortunately, there isn't much mentioned about data migration, especially data migration to S3. I thought that if I paste these four lines:
Liferay will move existing files automatically to Amazon S3. It doesn't and it can be easily misunderstood.
In fact user has to follow certain steps such as:
1. User has to set up these 3 properties in portal-ext.properties first:
2. RESTART application server where Liferay is deployed
3. perform data migration via Control Panel -> Server menu -> Server administration -> Data Migration
4. after successfull migration insert following property to portal-ext.properties:
-> after this step All data are migrated to Amazon S3 and Lifery is ready to be used with Amazon S3 repository.
If we do data migration without restart application server (step 2), access to S3 isn't loaded, migration process fails and files are inaccessible. In that case user has to remove dl.store.impl=com.liferay.portlet.documentlibrary.store.S3Store property again (or change it to previous settings) and restart application server, otherwise files will not be accessible even after restart. After restart files are again available and user can perform proper migration.
More information can be found on issue https://issues.liferay.com/browse/LPS-36105 .
Or in blog http://blog.profiq.cz/2013/06/24/setup-amazon-s3-to-liferay-with-data-migration/