Hadoop is an open-source software framework sponsored by Apache. Using the MapReduce programming model, it consists of computer clusters built from commodity hardware that distribute storage and processing of the dataset of big data. All the modules in Hadoop are designed with a fundamental assumption that hardware failures are common and should be handled automatically. Hadoop seems less intuitive as for use as a voice mail system, but it was designed for large datasets which is exactly what a large voice mail system (with millions of subscribers) is: a large data set of messages. Its usage of commodity hardware to create a fault tolerant file store while maintaining the flexibility of matching and replacing standard servers with new (or older) ones.
SAN provides access to consolidated, block level data storage and is primarily used to enhance storage devices such as disk arrays accessible to servers which enables devices to appear to the operating system as locally attached devices. A SAN typically has its own network of storage devices generally not accessible by other devices through the local area network (LAN). Voice mail systems that uses SQL databases to store all messages can benefit greatly from SAN storage. Attaching it to the SQL Server and placing the database on the SAN allows for flexibility in mirroring, or in clustering the servers themselves. The SAN offers redundancy by using purpose built controllers, power supplies and sets of RAID arrays.
NAS is a file-level computer data storage server connected to a computer network that provides data access to a heterogeneous group of clients. Specialized for serving files either by its hardware, software, or configuration, NAS is often manufactured as a computer appliance – a purpose-built specialized computer. These systems are networked appliances that contain one or more storage drives often arranged into logical, redundant storage containers, or RAID. Network-attached storage (NAS) removes the responsibility of file serving from other servers of the network and typically provides access to files using network file sharing protocols such as: NFS, SMB/CIFS, or AFP. Voice mail systems using a filesystem to store messages benefits from a NAS storage component by making all voice messages available to multiple servers. This method requires a system of storing the messages to appropriately matched drives that when accomplished facilitates the creation of a truly ‘highly available’ cluster of components
In the end, there may not be a right or a wrong disk storage architecture for voice mail as each has shown to have its own benefits. A flexible voice mail system built to use any of these technologies will help future proof you decision on a voice mail vendor.