Departmental workloads make up the bulk of NAS implementations . These workloads are defined as users and applications that are closely integrated in terms of physical office structure, network segments, or application usage. Most environments are a combination of all three of these attributes. This is characterized by a physical attribute such as all the engineers on the third and fourth floors, the entire set of architects within the building, or the customer support representatives in the basement . They share a common attribute in that they are physically located together and are serviced by servers that provide both network access and a shared storage space within that server, or a combination of servers supporting that physical area.
However, the physical factor may only exist in terms of network proximity, where all the sales people at the front of the building share a network segment with, say, the executive secretaries, and half of the customer service department, which is located in the basement. The common network segment provides an infrastructure again where these groups likely share file system servers that provide outside network access to the rest of the company as well as customers and shared files within their own organizational domains.
Certainly, many of the personnel with the same physical environment and network segment are going to share a common set of applicationsusually the ones directed by the corporation, installed by the IT department, and used by the sales and support representatives in the front of the office and the customer service representatives in the basement.
Common activities within the shared environment just discussed are the continual additions, upgrades, changes, and enhancements to the departmental file servers that service the network segment. This is driven for the most part by the growing demand for storage on the file servers. Even though the applications are upgraded and enhanced, physical growth must increase alongside the data accumulated by the sales department, administration, and, yes, the guys in the basement.
This continual upheaval becomes costly, disruptive, and inefficient, adding, replacing, and enhancing general-purpose servers to accommodate additional and more sophisticated storage, just to access files.
The solution is a NAS appliance.
The data organizational model has a file system bundled into the solution (yes, thats right, a file system). File processing characteristics are based upon the requirements that workloads place on the file system and supporting file transport protocols. Characterizations of file system processing complexities, including simple file processing (Sfp), quality file processing (Qfp), and complex file processing (Cfp) can be found in Chapter 12.
User traffic always plays a significant role in defining the number of paths needed on a concurrent basis for a particular workload. The I/O content of the users transactions compared to the total workload byte transfer rate will begin to determine the NetPaths required. These estimates are based upon the aggregate network speeds and the type and characteristics of the Network Interface Cards used in the proposed NAS solution.
Data paths must include the total number of paths that the data travels . Consequently, data paths are combined with the number of network paths from both servers and users (for instance, the NICs), and the number of SCSI channels for each storage array that has access to server processing.
Figure 19-4 shows an example of NAS appliance configurations supporting the departmental file server requirements.