A.o. Univ. Prof. Dr. Dipl.-Ing. eva Kühn
TU Wien

Florian Kruse

Use Cases For A Heterogeneous SQL-Database Cluster Via Virtual Shared Memory, Its Limits And Alternative Solutions


Diploma Thesis, TU-Vienna, 2011


These days software solutions constitute a critical part of business infrastructures. Almost all companies use at least one such solution, which is indispensable for the daily business. Therefore reliable solutions are needed, which are both highly available and ensure data consistency. There are many solutions providing these characteristics, but they target large enterprises. So, there is a need for inexpensive, simple solutions, which small companies can afford. (Kruse, 2010) developed a database cluster solution, that filled that gap.


Here this work is continued. This thesis analyzes on the basis of use cases the applicability and the limitations of such a heterogeneous SQL cluster and, more general, of highly available database solutions. The limitations are for example found in the software components surrounding the database. Business software systems are most often too large and too complex, such that a data base solution alone is not sufficient for guaranteeing high availability. For each presented use case possible solutions are discussed. The applied high availability methods exceed the usual methods, as for example RAID or operation systems clusters, and contrast the emerging technologies virtualization and outsourcing to data centers or the cloud. In the last year unavailability of large cloud computing services and massive data thefts emphasized the need for turning to alternatives which keep the data within the company.


This thesis shows the risks relevant to high availability solutions involving databases. Furthermore it is shown that by using a good software design and a well thought-through system architecture it is possible for small enterprises to have affordable high availability solutions, which keep the data sovereignty within the company and without creating additional dependencies on internet connections or on intransparent services.


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