What is DFS – Distributed File System? (Benefits Explained)
What is DFS – Distributed File System? (Benefits Explained). A Distributed File System (DFS) is a file system that allows users to access file storage from several hosts via a computer network as if the client was accessing local storage. It allows programs to access and store remote data in the same way as local files. In addition, it enables users to access files from any computer or network system. Additionally, it permits network users to share files and information in a permitted and regulated manner. In a DFS, the servers control the data and give users access control.
Well, the primary purpose of DFS is to allow users of physically distributed systems to share their information and resources using a Common File System (CFS). Also a DFS file system runs as part of the operating system. Its configuration is a collection of mainframes and workstations that a local area network connects. In DFS, creating a namespace is visible to the users.
Shall we start with What is DFS – Distributed File System? (Benefits Explained).
How Does a DFS Work?
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Basically, DFS allows you to logically share data and resources on various servers. Hence, it enables you to join the group shares into one hierarchical namespace transparently. Certainly, DFS uses a treelike structure to organize shared resources on a network. It supports one host server namespaces, standalone DFS namespaces, and domain based namespaces with high availability and multiple host servers. The Active Directory stores the domain based namespace topology data. This data includes the DFS links, DFS targets, and DFS root.
Every DFS tree structure contains a single or multiple root target. A root target is a host server that executes the DFS service. Each tree structure has one or multiple DFS links. All of the DFS links point to one or several shared folders. Users add, delete and modify DFS links from a namespace.
Additionally, a DFS link leads to single or multiple shared folders known as targets. Once a user gains access to a DFS link, the DFS server chooses a collection of targets depending on a client’s site data. The clients access the first available target in the collection. This helps in distributing client requests across possible targets. Also, it offers uninterrupted access for users even if some servers fail.
What are the Components of DFS?
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A DFS has two main components:
- Location Transparency– The namespace component achieves location transparency.
- Redundancy– Redundancy achieves through a file synchronization/replication component.
In the event of heavy load or failure, the two components work together to improve data availability. They enable the sharing of data from multiple locations to be logically grouped under a single folder, referred to as the DFS root.
It is not necessary to use both DFS components simultaneously. Users can employ the namespace component without using the file replication component. On the other end, clients use the file replication component between servers without using the namespace component.
Implementations of Distributed File System
Consequently, a DFS system is designed to enable users to share data and files from a common file system. Here are the main implementations of DFS:
Hadoop
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Hadoop is a suite of open-source technologies that employs the MapReduce programming style to provide distributed management and storage of large amounts of data. It contains a storage component called Hadoop Distributed File System (HDFS).In nutshell, a functional component based on the MapReduce programming model.
Network File System
The (NFS) Network File System is a structure for storing files on a network. It allows clients to access directories and files located on isolated computers and handle those directories and files as if they were local. For instance, clients apply operating system commands to write, read, set, create, and remove file attributes for isolated directories and files.
Common Internet File System (CIFS)
Equally, CIFS is a public iteration of the Server Message Block file that IBM developed for use across the internet. Basically, it is an isolated file system protocol that allows clusters to share documents and collaborate within corporate intranets or over the internet.
CIFS is an open, multi-platform technology based on Microsoft Windows platforms’ native file-sharing protocols. Various platforms, such as UNIX, support CIFS. It supports Unicode filenames; users can employ it to mount an isolated file system as a drive or directory on the local machine. CIFS also has features not supported by NFS, such as native support for locks and write-ahead.
Server Message Block (SMB)
The Server Message Block (SMB) is a file sharing protocol that enables computer applications to request services from server programs and read and write to files in a computer network. Clients use the SMB protocol, its TCP/IP protocol, and other network protocols. With the SMB protocol, the users of an application access resources or files from a remote server. Then, SMB also communicates with server programs that accepts SMB client requests.
NetWare
Netware is a computer network operating system created by Novell, Inc. Although NetWare is no longer in use, clients originally used it for cooperative multitasking to execute several services on a personal PC with the IPX network protocol. Netware is suitable for use by companies downsizing from mainframe to PC network. It has memory protection and a low hardware requirement.
Up next with What is DFS – Distributed File System? (Benefits Explained) is to learn the main features of DFS.
Key Features of DFS
DFS has a variety of features. These include:
Transparency
Transparency is a security mechanism to protect a file system from other files and users. DFS has four types of transparency:
- Structure Transparency- The user is not required to know the location or number of file servers and storage devices. In structure transparency, multiple file servers must be able to adapt, and perform.
- Naming Transparency. There should be no trace of the file’s location within the file’s name. When a client moves a file from one node to another, the file name should not change
- Access Transparency. Both local and isolated files have to be accessible in the same way. The file system has to automatically find the accessed file and send it to the client
- Application Transparency. When clients copy a file across multiple nodes, they must hide the file copies and their locations from one node to the next.
Scalability
The distributed system increases over time as clients incorporate more machines into the network or when two networks link together. A good DFS must be able to scale quickly as the system’s number of users and nodes increases.
Data Integrity
Since many users typically share a file system, the file system needs to safeguard the integrity of the data stored in a transferred file. A concurrency control approach has to accurately synchronize concurrent access requests from multiple users vying to access the same file. A suitable file system offers users atomic transactions with high-level concurrency systems to ensure data integrity.
High Reliability
An effective DFS must reduce the possibility of data loss as much as possible. Users should not feel compelled to create backups of their files because of system unreliability. Rather a file system must back up important files to be restored if something happens to the originals. To improve reliability, a lot of file systems employ stable storage.
High Availability
A good DFS should be able to function in the event of a partial failure, such as link failure, storage device crash, and node failure.
Ease of Use
The user interface of a file system in multiprogramming should be simple, with minimal commands in the file.
Difference between DFS Replication and DFS Namespaces
DFS consists of two main role services; Replication and Namespaces:
Replication
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DFS Replication is a windows server role service that enables the user to replicate folders across several sites and servers. This includes those associated with a DFS namespace path. Ideally, it is a multiple master and efficient replication engine that you can use to achieve synchronization among servers over limited bandwidth network connections. DFS Replication takes the place of the File Replication Service as the DFS Namespaces replication engine.
Evidently, DFS replication makes use of a compression algorithm by the name of remote differential compression RDC. RDC identifies changes to data within a file and allows DFS Replication to replicate the altered file blocks instead of the whole file. To use this replication, users have to create replication groups and include replicated folders in the groups.
What is a DFS Namespace?
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A Distributed File System (DFS) Namespaces is a virtual folder or role service that allows users to group share folders that are on different servers into one or multiple logically structured namespaces. This lets users view shared folders virtually, where an individual path points to files on various servers.
Components of a DFS Namespace
Namespace server – This is a (VM) or the physical server that hosts a DFS namespace. A namespace server can be a domain controller or an ordinary server with the DFS role installed.
Namespace root– This is the starting point of the DFS namespace tree.
Folder– This is a link in the DFS namespace that leads to a target folder that contains content for users’ access. There are also folders without folder targets used to organize the structure and hierarchy.
Folder targets– A folder target is a link to a group-shared namespace or folder located on a specific file server and available through the Universal Naming Convention (UNC). A single folder target can be a link to one or more folders if they are located on two disparate servers and replicated with each other.
DFS Namespace Implementations
DFS has two main methods of implementation, and these are:
- Standalone DFS Namespace, which stores configuration metadata and information locally on a root server within the system registry. The path to access the root namespace starts with the root server name. A standalone DFS namespace is not fault-tolerant and resides only on one server. If a root server is inaccessible, the entire DFS namespace is inaccessible.
2. Domain-based DFS Namespace, which stores configuration information and metadata in the active directory. A path to access a root namespace typically starts with the domain name. Users can store domain-based DFS namespace on several servers to improve the namespace availability. This method enables users to provide load balancing and fault tolerance across servers.
Benefits of DFS
Thanks to its wide variety of features and powerful, DFS offer numerous benefits over non distributed file systems and other file systems. Below are some of the benefits of DFS.
Faster Restarts and Improved Reliability
It is faster to restart a DFS after an abnormal shutdown using DCE LFS. This is because DCE LFS logs information affecting operations that affect the metadata associated with DCE LFS file sets and aggregates. Once a client restarts the system, DFS LFS replays logs to reconstruct the metadata. It restores the system to a constant state that is faster compared to non-LFS file systems that have to execute the fsck command.
Access to resources is much more reliable in DFS for various reasons. In a distributed file system, several clients, like the Cache Manager, can try to access similar data simultaneously. DFS uses tokens to ensure that users consistently work with the most recent copy of a file and track who is currently working with the file. Tokens pinpoint operations the client can perform on the data. They also function as a promise from the file exporter to notify the user if the centrally saved copy of the data changes; After such notification, the user can retrieve the newest copy of the data the next time it is requested.
DFS also increases the reliability of data access by enabling users to replicate the most commonly used DCE LFS fileset on several File Server machines. When users replicate the fileset, they place an exact copy of the fileset on a disparate File Server machine. The unavailability of a single server that hosts the fileset does not disrupt work on that fileset since the fileset is accessible from other machines.
Better Recovery from Failure
In most UNIX file systems, recovery from system failure involves running the fsck command. This ensures there are no corrupted file systems. Besides, it rectifies those that occur so that they do not affect the entire file system. In DFS, such measures are not necessary at every restart. When required, they use the DFS Salvager to find and correct severe data corruption that DCE LFS cannot recover without help. In some cases, problems may arise in the basic structure of the file system, or the log may be damaged. The Salvager allows users to check the file system and correct issues to avoid corruption of the whole DCE LFS aggregate, which contains the file system.
Once a user restarts the File Server machine, the File Exporter tries to restore consistent access to data within the machine. After the restart, it stops all clients from establishing new tokens for data on the machine for a short time. During this recovery period, the File Exporter honors requests to reestablish tokens from a user that held them before the restart. These users have the chance to recover their tokens before another user can request conflicting tokens—enabling users to regain their tokens after a file server machine restart is known as token state recovery.
Increased File Availability, Network Efficiency, and Access Time
Improved network efficiency and file availability in DFS is offered through three mechanisms: caching, replication, and multihomed file servers.
- Locally data caching reduces access time to the data. The cache is a region of a client machine’s memory or local disk dedicated to temporary data storage. When data is cached, subsequent access to the data is quicker since the client is not required to send a request across the network. So, caching reduces network traffic.
- Multihomed File Servers increase file availability and help administrators efficiently use their networks. Enabling administrators to build connections between subnetworks and the file servers increases Network efficiency. Several network connections per File Server also improve file availability since a problem in one network area is unlikely to make a File Server unavailable.
- Replication improves file availability by enabling DCE LFS filesets to be replicated on several server machines; this reduces the effects of machine outages.
File Location, Transparency, and Efficient Load Balancing
Compared to standard non distributed file systems, data load balancing is more efficient in DFS. One reason for this is the use of replication, which enables DCE LFS file sets from the most commonly used DCE LFS filesets to be spread across different machines, ensuring that no single machine becomes overloaded with data requests.
Multihomed server capability allows each machine to have several connections to the network, enabling direct connections to the subnetworks with the most requests. These connections help to minimize cross-router traffic.
Increased Interoperability and Scalability
It is possible to use data from non-LFS systems with DFS. Users can export a non-LFS disk partition to the DCE namespace to be used by clients as an aggregate in DCE. Although an exported section is accessible in the namespace, it holds only the one file system it contained when the client shipped it. Also, a non-LFS aggregate might not support features such as DCE ACLs, logged information about metadata, and fileset replication.
The Basic Overseer Server (BOS Server) in DFS automatically monitors DFS processes on file server machines. Upon being started and configured, the Basic Overseer Server continues to monitor DFS server processes with minimal intervention from the system administrator. Reduced administrative obligations with a high client-to-server ratio and performance make DFS a scaleable system. Users can add client and server machines to a DFS configuration with minimal impact on other clients or servers and with little additional administrative responsibilities.
Thank you for reading What is DFS – Distributed File System? (Benefits Explained). We shall conclude.
What is DFS – Distributed File System? (Benefits Explained) Conclusion
Summarizing, DFS is a valuable mechanism that helps to not only protect data but also deliver high availability and fault tolerance. These features make it ideal for a wide range of use cases, especially workloads that require extensive reads and writes. Also, it’s ideal for data-intensive jobs such as machine learning, computer simulations, and log processing.
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