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There are three additional areas in the home directory that are of concern. The configuration triple store (tdbModels) is addressed below. Solr indexes are addressed above. The upload directory stores thumbnails for people, etc. If you allowing real-time upload of photos, this directory needs to be on a shared HA filesystem. If you are only batch ingesting thumbnails from external sources, then syncing the directory across servers could suffice. If you are simply linking to externally hosted images, the uploads folder will not be a concern.

Content triple store

By default, this is SDB, stored in MySQL.  An HA MySQL configuration should permit multiple application servers to access the same MySQL server clusterthe content triple store is TDB, stored in the tdbContentModels folder in the home directory. TDB requires that you only have one JVM accessing a TDB triple store. Replication is not possible while the TDB files are open. There are two potential solutions.  Through disciplined system administration you may find that the material in the content triple store can be considered static.  The triple store can then be replicated across each server using a copy. 

A second approach would involve storing the content triple store using SDB in an HA MySQL cluster -  Configuration of Jena SDB and MySQL.

Configuration triple store

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