Modern Distributed Filesystems For Linux: An Introduction - page 3
What Are Distributed Filesystems?
Using a distributed filesystem introduces new commands and new concerns for system administrators, but also simplifies many standard administrative tasks. Distributed computing environments typically enable users to log in on any workstation within an administrative domain. This requires that the login, or authentication, mechanism, also be network-aware. In distributed filesystem environments, password and group files located on individual machines must be secondary to networked authentication mechanisms. A network-aware authentication mechanism, such as Kerberos or NIS, provides users the flexibiltiy to use any workstation, while standard machine-specific authentication mechanisms must still exist so that administartors can log in on individual machines to repair them or perform administrative tasks.
Storing shared data on centralized file servers rather than on individual desktop systems simplifies administrative tasks such as backing up and restoring files and directories. It also centralizes standard storage administration tasks such as monitoring filesystem use, and introduces new possibilities for storage management, such as load balancing. Distributed filesystems such as OpenAFS and Coda provide built-in logical volume management systems that enable administrators to move heavily-used volumes to more powerful or lightly-used machines. If the distributed filesystem supports replication, copies of heavily-used volumes can be distributed across multiple fileservers for use by different clients. This can reduce network use and lighten the load on specific servers. By using logical volumes rather than disk-specific physical volumes, distributed filesystems can also make it easy to add storage to your computing environment while your systems are running, without requiring downtime.
Using a distributed filesystem also makes it easier to share access to software, though you have to make sure that your software licenses enable you to install software into a distributed filesystem. Like the print servers that were part of the original motivation for client/server computing, distributed filesystems also simplify sharing access to specialized hardware by connecting to the system that hosts the hardware over the network and still being able to see all your files and data.
Using a centralized distributed filesystem can provide significant cost and performance benefits for client systems. Distributed filesystems substantially reduce hardware costs by minimizing the type and amount of storage that is required on any desktop or laptop workstation. Using a distributed filesystem as the repository for user data usually means faster client restart times because much of the data is no longer stored locally and therefore does not have to be checked for filesystem consistency after restarting a client. The combination of a distributed filesystem using a journaling filesystem for all or most of the filesystems local to client systems can provide additional improvements in system restart times.