4e - Discuss Distributed Databases

4e - Discuss Distributed Databases

1. Storage

   • Partitioned
     • Less storage needed centrally
     • Storage can split across sites
     • Increases storage capacity
   • Replicated
     • Lots of storage required at each site
   • Centralised
     • Storage only required once
     • Needs to be high quality
       • Fast access required
       • Multi-user access
     • Powerful processing required

2. Database design & local control

   • Partitioned
     • Each site can customise its database
     • Needs to be done in a controlled manner
       • Or data could become unavailable
   • Replicated
     • Each site can customise its database
       • Extra fields could be added
       • Must still be able to receive and send updates
   • Centralised
     • Still have no control over configuration
     • Database is configured centrally
     • Configured in a structured manner
       • So there will be no problems with integrity

3. Queries

   • Partitioned
     • Local queries are quick as data is stored locally
     • Global queries take longer as communication links are involved
   • Centralised
     • Data that exists in a local index
       • Queries are resonably quick
         • Search takes place locally
         • Data is retrieved centrally
     • Data not in the index
       • Queries are slower
         • Request is sent over communication link
         • Processing is done at central server
   • Replicated
     • All queries are quick as data is stored locally