Clustered file system

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A clustered file system (CFS) is a file system which is shared by being simultaneously mounted on multiple servers. There are several approaches to clustering, most of which do not employ a clustered file system (only direct attached storage for each node). Clustered file systems can provide features like location-independent addressing and redundancy which improve reliability or reduce the complexity of the other parts of the cluster. Parallel file systems are a type of clustered file system that spread data across multiple storage nodes, usually for redundancy or performance. [1]

Contents

Shared-disk file system

A shared-disk file system uses a storage area network (SAN) to allow multiple computers to gain direct disk access at the block level. Access control and translation from file-level operations that applications use to block-level operations used by the SAN must take place on the client node. The most common type of clustered file system, the shared-disk file system –by adding mechanisms for concurrency control  –provides a consistent and serializable view of the file system, avoiding corruption and unintended data loss even when multiple clients try to access the same files at the same time. Shared-disk file-systems commonly employ some sort of fencing mechanism to prevent data corruption in case of node failures, because an unfenced device can cause data corruption if it loses communication with its sister nodes and tries to access the same information other nodes are accessing.

The underlying storage area network may use any of a number of block-level protocols, including SCSI, iSCSI, HyperSCSI, ATA over Ethernet (AoE), Fibre Channel, network block device, and InfiniBand.

There are different architectural approaches to a shared-disk filesystem. Some distribute file information across all the servers in a cluster (fully distributed). [2]

Examples

Distributed file systems

Distributed file systems do not share block level access to the same storage but use a network protocol. [3] [4] These are commonly known as network file systems, even though they are not the only file systems that use the network to send data. [5] Distributed file systems can restrict access to the file system depending on access lists or capabilities on both the servers and the clients, depending on how the protocol is designed.

The difference between a distributed file system and a distributed data store is that a distributed file system allows files to be accessed using the same interfaces and semantics as local files – for example, mounting/unmounting, listing directories, read/write at byte boundaries, system's native permission model. Distributed data stores, by contrast, require using a different API or library and have different semantics (most often those of a database). [6]

Design goals

Distributed file systems may aim for "transparency" in a number of aspects. That is, they aim to be "invisible" to client programs, which "see" a system which is similar to a local file system. Behind the scenes, the distributed file system handles locating files, transporting data, and potentially providing other features listed below.

History

The Incompatible Timesharing System used virtual devices for transparent inter-machine file system access in the 1960s. More file servers were developed in the 1970s. In 1976, Digital Equipment Corporation created the File Access Listener (FAL), an implementation of the Data Access Protocol as part of DECnet Phase II which became the first widely used network file system. In 1984, Sun Microsystems created the file system called "Network File System" (NFS) which became the first widely used Internet Protocol based network file system. [4] Other notable network file systems are Andrew File System (AFS), Apple Filing Protocol (AFP), NetWare Core Protocol (NCP), and Server Message Block (SMB) which is also known as Common Internet File System (CIFS).

In 1986, IBM announced client and server support for Distributed Data Management Architecture (DDM) for the System/36, System/38, and IBM mainframe computers running CICS. This was followed by the support for IBM Personal Computer, AS/400, IBM mainframe computers under the MVS and VSE operating systems, and FlexOS. DDM also became the foundation for Distributed Relational Database Architecture, also known as DRDA.

There are many peer-to-peer network protocols for open-source distributed file systems for cloud or closed-source clustered file systems, e. g.: 9P, AFS, Coda, CIFS/SMB, DCE/DFS, WekaFS, [7] Lustre, PanFS, [8] Google File System, Mnet, Chord Project.

Examples

Network-attached storage

Network-attached storage (NAS) provides both storage and a file system, like a shared disk file system on top of a storage area network (SAN). NAS typically uses file-based protocols (as opposed to block-based protocols a SAN would use) such as NFS (popular on UNIX systems), SMB/CIFS (Server Message Block/Common Internet File System) (used with MS Windows systems), AFP (used with Apple Macintosh computers), or NCP (used with OES and Novell NetWare).

Design considerations

Avoiding single point of failure

The failure of disk hardware or a given storage node in a cluster can create a single point of failure that can result in data loss or unavailability. Fault tolerance and high availability can be provided through data replication of one sort or another, so that data remains intact and available despite the failure of any single piece of equipment. For examples, see the lists of distributed fault-tolerant file systems and distributed parallel fault-tolerant file systems.

Performance

A common performance measurement of a clustered file system is the amount of time needed to satisfy service requests. In conventional systems, this time consists of a disk-access time and a small amount of CPU-processing time. But in a clustered file system, a remote access has additional overhead due to the distributed structure. This includes the time to deliver the request to a server, the time to deliver the response to the client, and for each direction, a CPU overhead of running the communication protocol software.

Concurrency

Concurrency control becomes an issue when more than one person or client is accessing the same file or block and want to update it. Hence updates to the file from one client should not interfere with access and updates from other clients. This problem is more complex with file systems due to concurrent overlapping writes, where different writers write to overlapping regions of the file concurrently. [9] This problem is usually handled by concurrency control or locking which may either be built into the file system or provided by an add-on protocol.

History

IBM mainframes in the 1970s could share physical disks and file systems if each machine had its own channel connection to the drives' control units. In the 1980s, Digital Equipment Corporation's TOPS-20 and OpenVMS clusters (VAX/ALPHA/IA64) included shared disk file systems. [10]

See also

Related Research Articles

Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun) in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call system. NFS is an open IETF standard defined in a Request for Comments (RFC), allowing anyone to implement the protocol.

The Andrew File System (AFS) is a distributed file system which uses a set of trusted servers to present a homogeneous, location-transparent file name space to all the client workstations. It was developed by Carnegie Mellon University as part of the Andrew Project. Originally named "Vice", "Andrew" refers to Andrew Carnegie and Andrew Mellon. Its primary use is in distributed computing.

<span class="mw-page-title-main">Network-attached storage</span> Computer data storage server

Network-attached storage (NAS) is a file-level computer data storage server connected to a computer network providing data access to a heterogeneous group of clients. The term "NAS" can refer to both the technology and systems involved, or a specialized device built for such functionality.

In computing, the Global File System 2 or GFS2 is a shared-disk file system for Linux computer clusters. GFS2 allows all members of a cluster to have direct concurrent access to the same shared block storage, in contrast to distributed file systems which distribute data throughout the cluster. GFS2 can also be used as a local file system on a single computer.

<span class="mw-page-title-main">File system</span> Computer filing system

In computing, a file system or filesystem governs file organization and access. A local file system is a capability of an operating system that services the applications running on the same computer. A distributed file system is a protocol that provides file access between networked computers.

Google File System is a proprietary distributed file system developed by Google to provide efficient, reliable access to data using large clusters of commodity hardware. Google file system was replaced by Colossus in 2010.

GPFS is high-performance clustered file system software developed by IBM. It can be deployed in shared-disk or shared-nothing distributed parallel modes, or a combination of these. It is used by many of the world's largest commercial companies, as well as some of the supercomputers on the Top 500 List. For example, it is the filesystem of the Summit at Oak Ridge National Laboratory which was the #1 fastest supercomputer in the world in the November 2019 Top 500 List. Summit is a 200 Petaflops system composed of more than 9,000 POWER9 processors and 27,000 NVIDIA Volta GPUs. The storage filesystem is called Alpine.

In database computing, Oracle Real Application Clusters (RAC) — an option for the Oracle Database software produced by Oracle Corporation and introduced in 2001 with Oracle9i — provides software for clustering and high availability in Oracle database environments. Oracle Corporation includes RAC with the Enterprise Edition, provided the nodes are clustered using Oracle Clusterware.

The Parallel Virtual File System (PVFS) is an open-source parallel file system. A parallel file system is a type of distributed file system that distributes file data across multiple servers and provides for concurrent access by multiple tasks of a parallel application. PVFS was designed for use in large scale cluster computing. PVFS focuses on high performance access to large data sets. It consists of a server process and a client library, both of which are written entirely of user-level code. A Linux kernel module and pvfs-client process allow the file system to be mounted and used with standard utilities. The client library provides for high performance access via the message passing interface (MPI). PVFS is being jointly developed between The Parallel Architecture Research Laboratory at Clemson University and the Mathematics and Computer Science Division at Argonne National Laboratory, and the Ohio Supercomputer Center. PVFS development has been funded by NASA Goddard Space Flight Center, The DOE Office of Science Advanced Scientific Computing Research program, NSF PACI and HECURA programs, and other government and private agencies. PVFS is now known as OrangeFS in its newest development branch.

Gluster Inc. was a software company that provided an open source platform for scale-out public and private cloud storage. The company was privately funded and headquartered in Sunnyvale, California, with an engineering center in Bangalore, India. Gluster was funded by Nexus Venture Partners and Index Ventures. Gluster was acquired by Red Hat on October 7, 2011.

<span class="mw-page-title-main">Dell EMC Isilon</span> Network-attached storage

Dell EMC Isilon is a scale out network-attached storage platform offered by Dell EMC for high-volume storage, backup and archiving of unstructured data. It provides a cluster-based storage array based on industry standard hardware, and is scalable to 50 petabytes in a single filesystem using its FreeBSD-derived OneFS file system.

Ceph is a free and open-source software-defined storage platform that provides object storage, block storage, and file storage built on a common distributed cluster foundation. Ceph provides distributed operation without a single point of failure and scalability to the exabyte level. Since version 12 (Luminous), Ceph does not rely on any other conventional filesystem and directly manages HDDs and SSDs with its own storage backend BlueStore and can expose a POSIX filesystem.

Scale out File Services (SoFS) is a highly scalable, grid-based network-attached storage (NAS) implementation developed by IBM. It is based on IBM's high-performance shared-disk clustered file system Spectrum Scale. SoFS exports the clustered file system through industry standard protocols like Server Message Block, Network File System, File Transfer Protocol and Hypertext Transfer Protocol. Released in 2007, SoFS is a second generation file services architecture used within IBM since 2001.

Cluster Shared Volumes (CSV) is a feature of Failover Clustering first introduced in Windows Server 2008 R2 for use with the Hyper-V role. A Cluster Shared Volume is a shared disk containing an NTFS or ReFS volume that is made accessible for read and write operations by all nodes within a Windows Server Failover Cluster.

<span class="mw-page-title-main">Dell Fluid File System</span> Filesystem by Dell

Dell Fluid File System, or FluidFS, is a shared-disk filesystem made by Dell that provides distributed file systems to clients. Customers buy an appliance: a combination of purpose-built network-attached storage (NAS) controllers with integrated primary and backup power supplies attached to block level storage via the iSCSI or Fiber Channel protocol. A single Dell FluidFS appliance consists of two controllers operating in concert connecting to the back-end storage area network (SAN). Depending on the storage capacity requirements and user preference, FluidFS version 4 NAS appliances can be used with Compellent or EqualLogic SAN arrays. The EqualLogic FS7600 and FS7610 connect to the client network and to Dell's EqualLogic arrays with either 1 Gbit/s (FS7600) or 10 Gbit/s (FS7610) iSCSI protocol. For Compellent, FluidFS is available with either 1 Gbit/s or 10 Gbit/s iSCSI connectivity to the client network and connection to the backend Compellent SAN can be either 8 Gbit/s Fibre Channel or 10 Gbit/s iSCSI.

A distributed file system for cloud is a file system that allows many clients to have access to data and supports operations on that data. Each data file may be partitioned into several parts called chunks. Each chunk may be stored on different remote machines, facilitating the parallel execution of applications. Typically, data is stored in files in a hierarchical tree, where the nodes represent directories. There are several ways to share files in a distributed architecture: each solution must be suitable for a certain type of application, depending on how complex the application is. Meanwhile, the security of the system must be ensured. Confidentiality, availability and integrity are the main keys for a secure system.

LizardFS is an open source distributed file system that is POSIX-compliant and licensed under GPLv3. It was released in 2013 as fork of MooseFS. LizardFS is also offering a paid Technical Support with possibility of configurating and setting up the cluster and active cluster monitoring.

ONTAP, Data ONTAP, Clustered Data ONTAP (cDOT), or Data ONTAP 7-Mode is NetApp's proprietary operating system used in storage disk arrays such as NetApp FAS and AFF, ONTAP Select, and Cloud Volumes ONTAP. With the release of version 9.0, NetApp decided to simplify the Data ONTAP name and removed the word "Data" from it, removed the 7-Mode image, therefore, ONTAP 9 is the successor of Clustered Data ONTAP 8.

References

  1. ↑ Saify, Amina; Kochhar, Garima; Hsieh, Jenwei; Celebioglu, Onur (May 2005). "Enhancing High-Performance Computing Clusters with Parallel File Systems" (PDF). Dell Power Solutions. Dell Inc. Retrieved 6 March 2019.
  2. ↑ Mokadem, Riad; Litwin, Witold; Schwarz, Thomas (2006). "Disk Backup Through Algebraic Signatures in Scalable Distributed Data Structures" (PDF). DEXA 2006 Springer. Retrieved 8 June 2006.
  3. ↑ Silberschatz, Abraham; Galvin, Peter; Gagne, Greg (2009). "Operating System Concepts, 8th Edition" (PDF). University of Babylon. John Wiley & Sons, Inc. pp. 705–725. Archived from the original (PDF) on 6 March 2019. Retrieved 4 March 2019.
  4. 1 2 Arpaci-Dusseau, Remzi H.; Arpaci-Dusseau, Andrea C. (2014), Sun's Network File System (PDF), Arpaci-Dusseau Books
  5. ↑ Sandberg, Russel (1986). "The Sun Network Filesystem: Design, Implementation and Experience" (PDF). Proceedings of the Summer 1986 USENIX Technical Conference and Exhibition. Sun Microsystems, Inc. Retrieved 6 March 2019. NFS was designed to simplify the sharing of filesystem resources in a network of non-homogeneousmachines.
  6. ↑ Sobh, Tarek (2008). Advances in Computer and Information Sciences and Engineering. Springer Science & Business Media. pp. 423–440. Bibcode:2008acis.book.....S.
  7. ↑ "Weka Distributed File Systems (DFS)". weka.io. 2021-04-27. Retrieved 2023-10-12.
  8. ↑ "PanFS Parallel File System". panasas.com. Retrieved 2023-10-12.
  9. ↑ Pessach, Yaniv (2013). Distributed Storage: Concepts, Algorithms, and Implementations. ISBN   978-1482561043.
  10. ↑ Murphy, Dan (1996). "Origins and Development of TOPS-20". Dan Murphy. Ambitious Plans for Jupiter. Retrieved 6 March 2019. Ultimately, both VMS and TOPS-20 shipped this kind of capability.

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