A set of function calls that enables communication between applications or between an application and an operating system.
An AC power transfer switch. Its basic function is to deliver output power from one of two customer facility AC sources. It guarantees that the cluster will continue to function if a power failure occurs on one of the power sources by automatically switching to the secondary source.
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The Distinct Bit Sequence (DBS) of user data. The DBS represents the actual content of a file and is independent of the filename and physical location.
Note: Do not confuse this term with the term Binary Large Object that exists in the database sector.
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A package containing the user's data and associated metadata. When a user presents a file to the Centera system, the system calculates a unique Content Address (CA) for the data and then stores the file. The system also creates a separate XML file containing the CA of the user's file and application-specific metadata. Both the XML file and the user's data are stored in the C-Clip.
The additional XML file that the system creates when making a C-Clip. This file includes the Content Addresses for all referenced blobs and associated metadata.
The Content Address that the system returns to the client. It is also referred to as a C-Clip handle and C-Clip reference.
One or more racks whereby the nodes are clustered. Clustered nodes are automatically aware of nodes that attach to and detach from the cluster.
The synchronized time of all the nodes within a cluster.
A set of predefined commands that you can enter via a command line. The Centera CLI allows a user to manage a cluster and monitor its performance.
The log files of all nodes are consolidated into one time based log file.
An identifier that uniquely addresses the content of a file and not its location. Unlike location-based addresses, Content Addresses are inherently stable and, once calculated, they never change and always refer to the same content.
The process of discovering the IP address of a node containing a blob with a given Content Address.
The process of checking data integrity by comparing the CA calculations that are made on the application server (optional) and both Storage Nodes.
The generic term for a Centera cluster and its software. In the same way that a Symmetrix is considered a SAN device, a Centera is considered a CAS device.
The content protection scheme whereby each stored object is copied to another node on a Centera cluster to ensure data redundancy.
The content protection scheme whereby each object is fragmented into several segments that are stored on separate nodes with a parity segment to ensure data redundancy.
A collection of 8, 16, 24 or 32 computers and two switches, forming the basic building block for a cluster.
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The actual content of a file independent of the filename and physical location. Every file consists of a unique sequence of bits and bytes. The DBS of a user’s file is referred to as a blob in the Centera system.
An internet protocol used to assign IP addresses to individual workstations and peripherals in a LAN.
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Email Home allows the cluster to communicate with the EMC Customer Support Center via email. Email Home sends email messages to the EMC Customer Support Center via modems connected to the Centera itself or via a customer workstation with OnAlert installed on it.
The process of verifying data integrity from the application end down to the second Storage Node. See also Content Address Verification.
A flexible way to create common information formats and share both the format and the data on the World Wide Web, intranets, and elsewhere.
For more information, please refer to http://www.xml.com.
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Commonly confused with failure. It actually means that a failure is transparent to the user because the system will fail over to another process to ensure completion of the task; for example, if a disk fails, then the system will automatically find another one to use instead.
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The historic reporting feature will keep historical data on the local machine and allows the user to access the data at a later time (displayed in graphics).
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The required or optional information that has to be supplied to a function.
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The process of selecting the least-loaded node for communication. Load balancing is provided in two ways: first, an application server can connect to the cluster by selecting the least-loaded Access Node; second, the Access Node selects the least loaded Storage Node to read or write data.
A set of linked computers and peripherals in a restricted area such as a building or company.
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A unique 128-bit number that is calculated by the Message Digest 5-hash algorithm from the sequence of bits (DBS) that constitute the content of a file. If a single byte changes in the file then any resulting MD5 will be different.
A logical organization of a number of nodes that always mirror each other.
A network protocol used for communication between a single sender and multiple receivers.
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Logically, a network entity that is uniquely identified through a system ID, IP address, and port. Physically, a node is a computer system that is part of the Centera cluster.
The nodes in a cluster that communicate with the outside world. They must have public IP addresses. For clusters with CentraStar 2.3 and lower this was referred to as Access Node.
The nodes in a cluster that store data. For clusters with CentraStar 2.3 and lower this was referred to as Storage Node.
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The information that a function returns to the application that called the function.
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A set of separate clusters that are linked together to constitute one Content Addressed Storage device.
A further evolution of the UniCast Protocol (UCP) used for communication over the Internet between the application server and an Access Node.
A process where the application server requests information from the cluster to determine if it should start a PTP session.
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A process where data objects are duplicated or encoded such that the data can be recovered given any single failure. Refer to Content Protection Mirrored (CPM), Content Protection Parity (CPP), and Replication for specific redundancy schemes used in Centera.
The process of creating a data copy if a mirror copy or fragmented segment of that data is no longer available.
A way of streaming data directly from a Storage Node over an Access Node to the application server in case the Access cache does not contain the requested data.
The process of copying a blob to another cluster. This complements Content Protection Mirrored and Content Protection Parity. If a problem renders an entire cluster inoperable, then the replica cluster can keep the system running while the problem is fixed.
The time that a C-Clip and the underlying blobs have to be stored before the application is allowed to delete them.
The outcome of a function that the system returns to the application calling the function.
The process of restoring data from a cluster to a replica cluster. When a cluster is available again after repair, data from the replica cluster has to be restored to the other cluster. The time required to complete a full restore depends on the amount of data stored on the cluster and on client access occurring on both clusters.
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The process of splitting very large files or streams into smaller chunks before storing them. Segmentation is an invisible client-side feature and supports storage of very large files such as rich multimedia.
A node without a role assignment. This node can become a node with the storage and/or access role.
See Node with the Storage Role.
Generalized input/output channels that provide a way to handle incoming and outgoing data without having to know where that data comes from or goes to.
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The time between the request to the system to retrieve a C-Clip and the retrieval of the first byte of the blob.
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A network protocol used for communication between multiple senders and one receiver.
A standard Internet protocol used for the transport of data.
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A set of linked computers and peripherals that are not in one restricted area but that can be located all over the world.
A technique that stores data that does need to be regularly accessed, for example, a tape device.
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