In modern businesses, the design of file servers is complicated by competing demands for storage space, access speed,
recoverability, ease of administration,
security, and budget. This is further complicated by a constantly changing environment, where new hardware and technology rapidly obsolesces old equipment, and yet must seamlessly come online in a fashion
compatible with the older machinery. To manage
throughput, peak loads, and
response time,
vendors may utilize queuing theory to model how the combination of hardware and software will respond over various levels of demand. Servers may also employ dynamic
load balancing scheme to distribute requests across various pieces of hardware. The primary piece of hardware equipment for servers over the last couple of decades has proven to be the
hard disk drive. Although other forms of storage are viable (such as
magnetic tape and
solid-state drives) disk drives have continued to offer the best fit for cost, performance, and capacity.
Storage Since the crucial function of a file server is storage, technology has been developed to operate multiple disk drives together as a team, forming a
disk array. A disk array typically has
cache (temporary memory storage that is faster than the magnetic disks), as well as advanced functions like
RAID and
storage virtualization. Typically disk arrays increase level of
availability by using redundant components other than RAID, such as
power supplies. Disk arrays may be consolidated or virtualized in a
SAN.
Network-attached storage Network-attached storage (NAS) is file-level
computer data storage connected to a
computer network providing data access to a
heterogeneous group of clients. NAS devices specifically are distinguished from file servers generally in a NAS being a
computer appliance – a specialized computer built from the ground up for serving files – rather than a general purpose computer being used for serving files (possibly with other functions). In discussions of NASs, the term "file server" generally stands for a contrasting term, referring to general purpose computers only. NAS devices are gaining popularity, offering a convenient method for sharing files between multiple computers. Potential benefits of network-attached storage, compared to non-dedicated file servers, include faster data access, easier administration, and simple configuration. NAS systems are networked
appliances containing one or more hard drives, often arranged into logical, redundant storage containers or
RAID arrays. Network Attached Storage removes the responsibility of file serving from other servers on the network. They typically provide access to files using network file sharing protocols such as
NFS, SMB/CIFS (
Server Message Block/Common Internet File System), or
AFP.
Security File servers generally offer some form of system security to limit access to files to specific users or groups. In large organizations, this is a task usually delegated to
directory services, such as
openLDAP, Novell's
eDirectory or Microsoft's
Active Directory. These servers work within the hierarchical computing environment which treat users, computers, applications and files as distinct but related entities on the network and grant access based on user or group credentials. In many cases, the directory service spans many file servers, potentially hundreds for large organizations. In the past, and in smaller organizations, authentication could take place directly at the server itself. ==See also==