Celerra

Last updated
EMC Celerra
Developer EMC Corporation
Type Storage server
Release date1996;25 years ago (1996) (as Symmetrix Network File Storage)
Discontinued2011
Successor EMC VNX
Related articlesEMC Clariion

Celerra is a discontinued [1] NAS device produced by EMC Corporation until 2011, available either as an integrated unit or as a NAS header which can be added to an independent EMC storage array such as a Clariion or a Symmetrix. It supports the SMB, NFS, FTP, NDMP, TFTP and MPFS protocols. A Celerra Unified Storage device use Clariion storage array as its storage layer and also provides iSCSI and Fibre Channel block-level storage.

Contents

It was introduced in October 1996 for the NAS market as "Symmetrix Network File Storage" and later renamed to Celerra. [2]

Celerra was promoted as a platform for virtualization; [3] optional features included de-duplication, replication, NDMP and storage tiering.

Celerra runs on real-time operating system called Data Access in Real Time (DART). DART is a modified UNIX embedded kernel (just 32Mb) with additional functionality like Fibre Channel driver for HBA and Bonding For Ethernet added to operate as a file server.

Celerra is based on the same X-blade architecture as the Clariion. It is available with a single data mover X-blade or with multiple data movers in an active-passive N+1 configuration.

Comparable to Celerra products are products from NetApp which offer similar features and protocol support, apart from the ability to use block-level Fibre Channel.

In 2011, EMC introduced the new VNX series of unified storage disk arrays intended to replace both Clariion and Celerra products. [4] In early 2012, Clariion and Celerra were discontinued.

Data Access in Real Time

Data Access in Real Time (DART)
Developer EMC Corporation
OS family Unix-like
Working stateCurrent
Source model Proprietary
Kernel type Real-time kernel

Data Access in Real Time (DART) is a real-time operating system used by EMC Celerra. It is a modified UNIX Kernel with additional functionality.

DART is an embedded, real-time, operating system comprising a modified UNIX kernel and dedicated file server software that together transfer files and multimedia data across a network using a variety of network protocols.

In Summary

DART file server software executes entirely in the kernel—a real-time kernel, the design of which is based on monotonic scheduling. The DART kernel environment is not a generic user-application environment. Instead, the DART kernel provides a run-time environment for the file service; an embedded, dedicated application. The DART file server software is linked with the kernel into a single system image that is loaded for execution at boot time.

The DART Software Architecture

DART is organized into seven layers. These layers handle all the data movement in DART, and all functionality in DART is directed at implementing the processes contained in these layers. Starting with the layer closest to the hardware and ending with the layer closest to the user interface, DART’s functionality is organized as follows :

Layers 1 – 4 comprise functions performed within the kernel. The programmer typically uses components limited to the higher numbered layers (5 and 6) to add data moving applications.

DART’s RPC framework component provides both client and server facilities, which are implemented over STREAMS, not sockets. DART acts as an RPC server in the context of NFS, and as an RPC client in the context of NIS.

DART External environment. The DART is designed to provide rapid data movement and information sharing across a variety of hardware platforms in a networked environment. All data transfers are either request-response (pull-type for file transfers) or streaming (push-type for multimedia data) with time-sharing, real-time, or isochronous characteristics.

RPC on DART

Two types of RPC are implemented on DART: traditional RPC, and ONC RPC. Due to DART’s multi-threaded architecture, traditional RPC has been implemented on DART with several modifications. For example, on a SUN OS, the RPC code generator, RPCGEN, assumes a single-threaded UNIX process that calls into the library directly. However, DART doesn’t have UNIX processes; but instead uses true multi-threading—that is, n threads pick up RPC messages as they come in. Therefore, when using traditional RPC in DART, an application must perform such functions as registering with the portmapper and extracting credentials and other security information from the message (or checking security without extracting).

Most of the responsibility falls on the application developer—thread creation, initialization, end point creation, initial create main loop, processing stream, reading message, and so on. The Collector, a general synchronizer (not particular to RPC) needs to be declared, whereas in ONCRPC, the collector is built in.

In addition, traditional RPC has a basic structure for receiving the message, but then the application developer must take it apart by means of xdr format and analyze it. In addition, the client-side is not fully implemented. Finally, while RPC is primarily a synchronous protocol, it is used asynchronously in DART in conjunction with mutexes, condition variables, and other types of locks.

DART implements RPC over both the User Datagram Protocol (UDP) and the Transport Control Protocol (TCP). Each application has a single UDP stream and one TCP stream per connection, with the common IP module acting as a multiplexer.

See also

Related Research Articles

The Internet protocol suite, commonly known as TCP/IP, is the set of communications protocols used in the Internet and similar computer networks. The current foundational protocols in the suite are the Transmission Control Protocol (TCP) and the Internet Protocol (IP).

In computer networking, the User Datagram Protocol (UDP) is one of the core members of the Internet protocol suite. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network. Prior communications are not required in order to set up communication channels or data paths.

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 standard defined in a Request for Comments (RFC), allowing anyone to implement the protocol.

Berkeley sockets is an application programming interface (API) for Internet sockets and Unix domain sockets, used for inter-process communication (IPC). It is commonly implemented as a library of linkable modules. It originated with the 4.2BSD Unix operating system, released in 1983.

An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking: the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest-level layer, the detailed definitions and purposes are different.

In computing, the Windows Sockets API (WSA), later shortened to Winsock, is a technical specification that defines how Windows network application software should access network services, especially TCP/IP. It defines a standard interface between a Windows TCP/IP client application and the underlying TCP/IP protocol stack. The nomenclature is based on the Berkeley sockets API model used in BSD for communications between programs.

Network-attached storage 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. NAS is specialized for serving files either by its hardware, software, or configuration. It is often manufactured as a computer appliance – a purpose-built specialized computer. NAS systems are networked appliances that contain one or more storage drives, often arranged into logical, redundant storage containers or RAID. 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, or AFP. From the mid-1990s, NAS devices began gaining popularity as a convenient method of sharing files among multiple computers. Potential benefits of dedicated network-attached storage, compared to general-purpose servers also serving files, include faster data access, easier administration, and simple configuration.

In computer networking, a network service is an application running at the network application layer and above, that provides data storage, manipulation, presentation, communication or other capability which is often implemented using a client–server or peer-to-peer architecture based on application layer network protocols.

TCP offload engine (TOE) is a technology used in network interface cards (NIC) to offload processing of the entire TCP/IP stack to the network controller. It is primarily used with high-speed network interfaces, such as gigabit Ethernet and 10 Gigabit Ethernet, where processing overhead of the network stack becomes significant.

The port mapper is an Open Network Computing Remote Procedure Call service that runs on network nodes that provide other ONC RPC services.

Twisted (software)

Twisted is an event-driven network programming framework written in Python and licensed under the MIT License.

In computer networking, STREAMS is the native framework in Unix System V for implementing character device drivers, network protocols, and inter-process communication. In this framework, a stream is a chain of coroutines that pass messages between a program and a device driver. STREAMS originated in Version 8 Research Unix, as Streams.

EMC NetWorker is an enterprise-level data protection software product from Dell EMC that unifies and automates backup to tape, disk-based, and flash-based storage media across physical and virtual environments for granular and disaster recovery.

A network socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network. The structure and properties of a socket are defined by an application programming interface (API) for the networking architecture. Sockets are created only during the lifetime of a process of an application running in the node.

WebNFS is an extension to the Network File System (NFS) for allowing clients to access a file system over the internet using a simplified, firewall-friendly protocol.

Multi Path File System

The Multi Protocol File System (MPFS) is a multi-path network filesystem technology developed and sold by EMC Corporation. MPFS is intended to allow hundreds to thousands of client computer nodes to access shared computer data with higher performance than conventional NAS file sharing protocols such as NFS.

The Stream Control Transmission Protocol (SCTP) is a computer networking communications protocol in the transport layer of the Internet Protocol Suite. Originally intended for Signaling System 7 (SS7) message transport in telecommunication, the protocol provides the message-oriented feature of the User Datagram Protocol (UDP), while ensuring reliable, in-sequence transport of messages with congestion control like the Transmission Control Protocol (TCP). Unlike UDP and TCP, the protocol provides multi-homing and redundant paths to increase resilience and reliability. SCTP is standardized by the Internet Engineering Task Force (IETF) in RFC 4960. The SCTP reference implementation was released as part of FreeBSD version 7, and has since been widely ported to other platforms.

NuttX is a real-time operating system (RTOS) with an emphasis on technical standards compliance and small size. Scalable from 8-bit to 64-bit microcontroller environments, the main governing standards in NuttX are from the Portable Operating System Interface (POSIX) and the American National Standards Institute (ANSI). Further standard application programming interfaces (APIs) from Unix and other common RTOSes are adopted for functions unavailable under these standards, or inappropriate for deeply embedded environments, such as a fork.

Dell EMC Unity is one of Dell EMC’s mid-range storage array product lines. It was designed from the ground up as the next generation midrange unified storage array after the EMC VNX and VNXe series, which evolved out of the EMC Clariion SAN disk array.

References

  1. "EMC Discontinues Clariion, Celerra Storage Lines". Archived from the original on 2012-07-12. Retrieved 2011-08-24.
  2. Press, Gil (September 6, 2016). "A Very Short History Of EMC Corporation". Forbes Magazine. Retrieved December 13, 2017.
  3. Celerra: Ideal choice for VMware Archived 2009-10-26 at the Wayback Machine , VMware.com
  4. EMC unveils new VNX unified storage EMC Press release