Glossary

!! Eucalyptus Glossary

-By Dan Adams

Quick links: A B  C  D  E F G  H  I  J  K L M  N  O  P  Q R S  T  U  V  W X Y  Z

A

Amazon Elastic Block Store (Amazon EBS): Provides block level storage volumes for use with Amazon EC2 instances. Amazon EBS volumes are off-instance storage that persists independently from the life of an instance. Amazon Elastic Block Store provides highly available, highly reliable storage volumes that can be attached to a running Amazon EC2 instance and exposed as a device within the instance. Amazon EBS is particularly suited for applications that require a database, file system, or access to raw block level storage. See [| EBS]

Arbitrator: A Eucalyptus service that runs in HA(high availability) mode that monitors connectivity between a user and a user-facing component (CLC, Walrus, and CC). An Arbitrator approximates reachability to a user. Each Arbitrator uses ICMP messages to periodically test reachability to an external entity (for example, a network gateway or border router) or to an external site (for example, google.com).[| Eucalyptus Installation Guide]

B

Block: A sequence of bytes or bits, having a nominal length (a block size). Data thus structured are said to be blocked. The process of putting data into blocks is called blocking. Blocking is used to facilitate the handling of the data-stream by the computer program receiving the data. Blocked data is normally read a whole block at a time. Blocking is almost universally employed when storing data to 9-track magnetic tape, to rotating media such as floppy disks, hard disks, optical discs and to NAND flash memory. Most file systems are based on a block device, which is a level of abstraction for the hardware responsible for storing and retrieving specified blocks of data, though the block size in file systems may be a multiple of the physical block size. [| read More]

Bridging: A forwarding technique used in packet-switched computer networks. Unlike routing, bridging makes no assumptions about where in a network a particular address is located. Instead, it depends on flooding and examination of source addresses in received packet headers to locate unknown devices. Once a device has been located, its location is recorded in a table where the source address is stored so as to avoid the need for further flooding. The utility of bridging is limited by its dependence on flooding, and is thus only used in local area networks. [| Wikipedia entry]

Bucket: A scalable, logical storage area, supported by the Amazon S3 service, in which a user or administrator can store files and directories in a cloud environment. [| Amazon Exerpt]

C

Cloud Controller (CLC): The entry-point into the cloud for administrators, developers, project managers, and end-users. The CLC queries other components for information about resources, makes high-level scheduling decisions, and makes requests to theCluster Controllers (CCs). As the interface to the management platform, the CLC is responsible for exposing and managing the underlying virtualized resources (servers, network, and storage). You can access the CLC through command line tools that are compatible with Amazon’s Elastic Compute Cloud (EC2) and through a web-based Dashboard. See [| Eucalyptus Installation Guide]

Cluster Controller (CC): A Eucalyptus component that generally executes on a machine that has network connectivity to both the machines running the Node Controllers (NCs) and to the machine running the CLC. CCs gather information about a set of node machines and schedules virtual machine (VM) execution on specific node controllers. The CC also manages the virtual machine networks. All Node Controllers associated with a single CC must be in the same subnet. See [| Eucalyptus Installation Guide]

D

Data store: A data repository of a set of integrated objects. These objects are modeled using classes defined in database schemas. Data store includes not only data repositories like databases, it is a more general concept that includes also flat files that can store data. See [| Wikipedia entry]

Deployment: Assembly or transformation of code from a packaged form to an operational working state. Moving from a temporary or development state to a permanent or desired state. See [| Wikipedia entry]

DNS (Domain Name System): A hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. A Domain Name Service translates queries for domain names (which are meaningful to humans) into IP addresses for the purpose of locating computer services and devices worldwide. See [| Wikipedia entry]

Dnsmasq: A lightweight DNS forwarder, DHCP and TFTP server, designed to provide DNS (and optionally DHCP and TFTP) services to a small-scale network. It can serve the names of local machines which are not in the global DNS. The DHCP server integrates with the DNS server and allows machines with DHCP-allocated addresses to appear in the DNS with names configured either in each host or in a central configuration file. Dnsmasq supports static and dynamic DHCP leases and BOOTP for network booting of diskless machines. See [| Wikipedia entry]

DRBD: Block devices designed as a building block to form high availability (HA) clusters. This is done by mirroring a whole block device via an assigned network. DRBD can be understood as network based raid-1. [| more DRBD information]

E

Elastic Block Store (EBS): Provides block level storage volumes for use with Amazon EC2 instances. Amazon EBS volumes are off-instance storage that persists independently from the life of an instance. Amazon Elastic Block Store provides highly available, highly reliable storage volumes that can be attached to a running Amazon EC2 instance and exposed as a device within the instance. Amazon EBS is particularly suited for applications that require a database, file system, or access to raw block level storage. See [| EBS]

EC2 cloud service: Amazon Elastic Compute Cloud (Amazon EC2) Is a web service that provides resizable computing capacity in the cloud. It is designed to make web-scale computing easier for developers. Amazon EC2’s simple web service interface allows you to obtain and configure capacity with minimal friction. It provides you with complete control of your computing resources and lets you run on Amazon’s proven computing environment. [| EC2]

Elastic IP addresses: Static IP addresses designed for dynamic cloud computing. An Elastic IP address is associated with your account, not a particular instance, and you control that address until you choose to explicitly release it. Unlike traditional static IP addresses, however, Elastic IP addresses allow you to mask instance or availability zone failures by remapping your public IP addresses to any instance associated with your account. Rather than waiting on a data technician to reconfigure or replace your host, or waiting for DNS to propagate to all of your customers, Amazon EC2 enables you to engineer around problems with your instance or software by programmatically remapping your Elastic IP address to a replacement instance. [| read more]

Eucalyptus: The world's most widely deployed cloud computing software platform for on-premise (private) Infrastructure as a Service clouds. It uses existing infrastructure to create scalable and secure cloud resources for compute, network and storage.

F

Failover: Automatic switching to a redundant or standby computer server, system, or network upon the failure or abnormal termination of the previously active application, server, system, or network. Failover and switchover are essentially the same operation, except that failover is automatic and usually operates without warning, while switchover requires human intervention. [| read more]

Feature set:A group of functions (capabilities, capacities, etc.) for a particular piece of software. [| read more]

Filter Table (MAC Address Table): A table that exists on a router or other network traffic device that stores the MAC addresses of clients that will be allowed to join the network. See about.com's “Enable MAC Address Filtering on Wireless Access Points and Routers”, [| read more]

Firewall: A device, set of devices, or software program designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass. See [| Wikipedia entry]

Framework: An abstraction in which software providing generic functionality can be selectively changed by user code, thus providing application specific software. It is a collection of software libraries providing a defined application programming interface (API). [| read more]

G

Gateway: A link to a larger set of resources. This may be a gateway IP address for a network interface on a router that leads to a larger network, or a link between two computer programs allowing them to share information and bypass certain protocols on a host computer.[| read more]

H

High Availability (HA): A system design approach and associated service implementation that ensures a prearranged level of operational performance will be met during a contractual measurement period. Users want their systems, for example wrist watches, hospitals, airplanes or computers, to be ready to serve them at all times. Availability refers to the ability of the user community to access the system, whether to submit new work, update or alter existing work, or collect the results of previous work. If a user cannot access the system, it is said to be unavailable. See[| Wikipedia entry]

Hybrid cloud: A type of cloud that combines computing resources (e.g., machines, network, storage, etc.) drawn from one or more public clouds and one or more private clouds at the behest of its users. See Learn about cloud computing, [| Eucalyptus subject matter]

Hypervisor: Also called a virtual machine manager, is a program that allows multiple operating systems to share a single hardware host. Each operating system appears to have the host's processor, memory, and other resources all to itself. However, the hypervisor is actually controlling the host processor and resources, allocating what is needed to each operating system in turn and making sure that the guest operating systems (called virtual machines) cannot disrupt each other. See [| read more]

I

IaaS (Infrastructure as a Service): A cloud style that provides access to collections of virtualized computer hardware resources, including machines, network, and storage. With IaaS, users assemble their own virtual cluster on which they are responsible for installing, maintaining, and executing their own software stack. See Learn about cloud computing, [| Eucalyptus Page]

Infrastructure: A combined set of hardware, software, networks, facilities, etc. (including all of the information technology), in order to develop, test, deliver, monitor, control or support IT services. Associated people, processes and documentation are not part of IT Infrastructure. See [| Wikipedia entry]

Internet Control Message Protocol (ICMP): One of the core protocols of the Internet Protocol Suite. It is chiefly used by the operating systems of networked computers to send error messages indicating, for example, that a requested service is not available or that a host or router could not be reached. ICMP can also be used to relay query messages. It is assigned protocol number 1. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute). See [| Wikipedia entry]

iSCSI (Internet Small Computer System Interface): An (IP)-based storage networking standard for linking data storage facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances. iSCSI can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval. The protocol allows clients (called initiators) to send SCSI commands (CDBs) to SCSI storage devices (targets) on remote servers. It is a Storage Area Network (SAN) protocol, allowing organizations to consolidate storage into data center storage arrays while providing hosts (such as database and web servers) with the illusion of locally-attached disks. See [| Wikipedia entry]

J

Java memory manager: An important component of the Java virtual machine and the Java language that handles garbage collection, memory allocation and deallocation. See Tuning Java's Memory Manager for High Performance Server Applications, [| read more]

K

Kernel: The main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components). See [| Wikipedia entry]

KVM (Kernel Based Virtual Machine): A full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko. KVM also requires a modified QEMU although work is underway to get the required changes upstream. Using KVM, one can run multiple virtual machines running unmodified Linux or Windows images. Each virtual machine has private virtualized hardware: a network card, disk, graphics adapter, etc. The kernel component of KVM is included in mainline Linux, as of 2.6.20. See main page, [| read more]

L

Language agnostic: Aspects of programming that are independent of any specific programming language. [| read more]

Layer-2 (data link layer): Layer 2 of the seven-layer OSI model of computer networking. The data link layer is the protocol layer that transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment. The data link layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the physical layer. Examples of data link protocols are Ethernet for local area networks (multi-node), the Point-to-Point Protocol (PPP), HDLC and ADCCP for point-to-point (dual-node) connections. See [| Wikipedia entry]

LDAP (Lightweight Directory Access Protocol): An application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network. Directory services may provide any organized set of records, often with a hierarchical structure, such as a corporate electronic mail directory. See Wikipedia entry

libvirt: An open source API, daemon and management tool for managing platform virtualization. It can be used to manage Linux KVM, Xen, VMware ESX and other virtualization technologies. Graphical interfaces use it, such as Virtual Machine Manager, as do command line interfaces (virsh), and higher level tools like oVirt.libvirt itself is a C library. See [| Wikipedia entry]

LVM (Logical Volume Manager): A logical volume manager for the Linux kernel; it manages disk drives and similar mass-storage devices, in particular large ones. "Volume" refers to a disk drive or partition. See [| Wikipedia entry]

M

Managed Mode: A networking mode in which you define a large network (usually private, unroutable) from which VM instances will draw their IP addresses. Eucalyptus maintains a DHCP server with static mappings for each VM instance that is created. You can define a number of security groups that you can apply network ingress rules to for any VM that runs within that network. When a user runs a VM instance, they specify the name of such a network that a VM is to be a member of, and Eucalyptus selects a subset of the entire range of IPs that other VMs in the same network can reside. See [| Eucalyptus Installation Guide]

N

Network address translation (NAT): The process of modifying IP address information in IP packet headers while in transit across a traffic routing device. See [| Wikipedia entry]

Network-attached storage (NAS): File-level data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements. NAS is often made as a computer appliance – a specialized computer built from the ground up for storing and serving files – rather than simply a general purpose computer being used for the role. See [| Wikipedia entry]

Network bridge: Connects multiple network segments at the data link layer (Layer 2) of the OSI model. In Ethernet networks, the term bridge formally means a device that behaves according to the IEEE 802.1D standard. A bridge and a switch are very much alike; a switch being a bridge with numerous ports. Switch or Layer 2 switch is often used interchangeably with bridge. See [| Wikipedia entry]

Node Controller (NC): A Eucalyptus component that executes on any machine that hosts VM instances. The NC controls VM activities, including the execution, inspection, and termination of VM instances. It also fetches and maintains a local cache of instance images, and it queries and controls the system software (host OS and the hypervisor) in response to queries and control requests from the CC. The NC is also responsible for the management of the virtual network endpoint. See [| Eucalyptus Installation Guide]

Network Time Protocol (NTP) A protocol designed to synchronize the clocks of computers over a network. NTP version 4, a significant revision of the previous NTP standard, is the current development version. See [| NTP main page]

O

Open Source Software: Software for which the source code can be freely shared. See [| Learn More]

ONTAPI: (also known as Data ONTAP APIs) Are used to access and manage the storage system. Data ONTAP APIs are invoked in the form of XML. You can use the HTTP, HTTPS, and Windows DCE/RPC protocols to query Data ONTAP APIs. Data ONTAP APIs can manage Setup and management of storage objects, Quota/user management, Device configuration, Discovery of devices, aggregates, and volumes, Monitoring the health of the storage system, disk/volume capacity, and performance, Alerts/notifications, License management, Security, Block protocols, Data backup and recovery, Data replication, Archival and compliance of data, and File access protocols. [|See What ONTAPI is]

openntpd: A free, easy to use implementation of the Network Time Protocol. It provides the ability to sync the local clock to remote NTP servers and can act as NTP server itself, redistributing the local clock. See [| Open NTP]

P

PaaS (Platform as a Service): A cloud style that provide access to a programming or runtime environment with scalable compute and data structures embedded in it. With PaaS, users develop and execute their own applications within an environment offered by the service provider. See Learn about cloud computing, [| Eucalyptus Page]

Private cloud: A type of cloud that give users immediate access to computing resources hosted within an organization's infrastructure. Users self-provision and scale collections of resources drawn from the private cloud, typically via web service interface, just as with a public cloud. However, because it is deployed within the organization's existing data center—and behind the organization's firewall—a private cloud is subject to the organization's physical, electronic, and procedural security measures and thus offers a higher degree of security over sensitive code and data. In addition, private clouds consolidate and optimize the performance of physical hardware through virtualization, and can thus markedly improve data center efficiency while reducing operational expense. [| Learn About Cloud Computing]

Public cloud: A type of cloud that provide access to computing resources for the general public over the Internet. The public cloud provider allows customers to self-provision resources typically via a web service interface. Customer's rent access to resources as needed on a pay-as-you-go basis. Public clouds offer access to large pools of scalable resources on a temporary basis without the need for capital investment in data center infrastructure. [| Learn About Cloud Computing]

Q

Query: A precise request for information retrieval with database and information systems. See [| Wikipedia entry]

R

Remote Desktop Protocol (RDP): A proprietary protocol developed by Microsoft, which provides a user with a graphical interface to another computer. The protocol is an extension of the ITU-T T.128 application sharing protocol. Clients exist for most versions of Microsoft Windows (including Windows Mobile), Linux, Unix, Mac OS X, Android, and other modern operating systems. By default the server listens on TCP port 3389. Microsoft currently refers to their official RDP server software as Remote Desktop Services, formerly "Terminal Services". Their official client software is currently referred to as Remote Desktop Connection, formerly "Terminal Services Client".

REST (Representational state transfer): A style of software architecture for distributed hypermedia systems such as the World Wide Web. REST-style architectures consist of clients and servers. Clients initiate requests to servers; servers process requests and return appropriate responses. See [| Wikipedia entry]

RHEL (Red Hat Enterprise Linux): A Linux-based operating system developed by Red Hat and targeted toward the commercial market. See [| read more]

Runtime Environment: As soon as a software program is executed, it is in a runtime state. In this state, the program can send instructions to the computer's processor and access the computer's memory (RAM) and other system resources. When software developers write programs, they need to test them in the runtime environment. Therefore, software development programs often include an RTE component that allows the programmer to test the program while it is running. See [| read more]

S

S3 cloud service: Amazon S3 is storage for the Internet. It is designed to make web-scale computing easier for developers. Amazon S3 provides a simple web services interface that can be used to store and retrieve any amount of data, at any time, from anywhere on the web. It gives any developer access to the same highly scalable, reliable, secure, fast, inexpensive infrastructure that Amazon uses to run its own global network of web sites. [| Learn more]

SaaS (Software as a Service): A cloud style that delivers access to collections of software application programs. SaaS providers offer users access to specific application programs controlled and executed on the provider's infrastructure. SaaS is often referred to as “Software on Demand.” See [| Learn About Cloud Computing]

SAN (Storage area network): A dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices to the operating system. See [| Wikipedia entry]

Secure Shell (SSH): A network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client (running SSH server and SSH client programs, respectively). The protocol specification distinguishes two major versions that are referred to as SSH-1 and SSH-2. The best-known application of the protocol is for access to shell accounts on Unix-like operating systems. See [| Wikipedia entry]

SOAP(Simple Object Access Protocol): A protocol specification for exchanging structured information in the implementation of Web Services in computer networks. It relies on Extensible Markup Language (XML) for its message format, and usually relies on other Application Layer protocols, most notably Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission. SOAP can form the foundation layer of a web services protocol stack, providing a basic messaging framework upon which web services can be built. See [| Wikipedia entry]

Storage Controller (SC): A Eucalyptus component that provides functionality similar to the Amazon Elastic Block Store (Amazon EBS). The SC is capable of interfacing with various storage systems (NFS, iSCSI, SAN devices, etc.). Elastic block storage exports storage volumes that can be attached by a VM and mounted or accessed as a raw block device. EBS volumes persist past VM termination and are commonly used to store persistent data. An EBS volume cannot be shared between Vms and can only be accessed within the same availability zone in which the VM is running. Users can create snapshots from EBS volumes. Snapshots are stored in Walrus and made available across availability zones. Eucalyptus with SAN support lets you use your enterprise-grade SAN devices to host EBS storage within a Eucalyptus cloud. See [| Eucalyptus Installation Guide]

Subnet (Subnetwork): A logically visible subdivision of an IP network. The practice of dividing a single network into two or more networks is called subnetting and the networks created are called subnetworks or subnets. See [| Wikipedia entry]

T

TCP/IP (Transmission Control Protocol/Internet Protocol): A descriptive framework for the Internet Protocol Suite of computer network protocols. TCP/IP provides end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination. Protocols exist for a variety of different types of communication services between computers. See [| Wikipedia entry]

U

User Datagram Protocol (UDP): Is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths. [| Wikipedia entry]

V

VLAN Trunking Protocol (VTP): A Cisco proprietary protocol that propagates the definition of Virtual Local Area Networks (VLAN) on the whole local area network. To do this, VTP carries VLAN information to all the switches in a VTP domain. VTP is available on most of the Cisco Catalyst Family products. See wikipedia entry at [| Wikipedia entry]

VMware Broker (Broker): Is an optional Eucalyptus component activated only in versions of Eucalyptus with VMware support. Broker enables Eucalyptus to deploy virtual machines (VMs) on VMware infrastructure elements. Broker mediates all interactions between the CC and VMware hypervisors (ESX/ESXi) either directly or through VMware vCenter. See [| Eucalyptus Installation Guide]

VMware ESX: An enterprise-level computer virtualization product offered by VMware, Inc. ESX is a component of VMware's larger offering, VMware Infrastructure, and adds management and reliability services to the core server product. The original ESX is being replaced by ESXi. VMware ESX and VMware ESXi are bare-metal embedded hypervisors that are VMware's enterprise software hypervisors for servers that run directly on server hardware without requiring an additional underlying operating system. See [| Wikipedia entry]

VMware ESXi: A smaller footprint version of ESX that does not include ESX's Service Console. It is available as a free download from VMware though certain features are disabled[26] without the purchase of a vCenter license. VMware ESXi was originally a compact version of VMware ESX that allowed for a smaller 32 MB disk footprint on the Host. With a simple configuration console for mostly network configuration and remote based VMware Infrastructure Client Interface, this allows for more resources to be dedicated to the Guest environments See [| Wikipedia entry]

VMware vSphere: VMware's cloud computing virtualization operating system. See [| Wikipedia entry]

Volume: The term used to describe a single accessible storage area with a single file system, typically (though not necessarily) resident on a single partition of a hard disk. Similarly, it refers to the logical interface used by an operating system to access data stored on some media using a single instance of a filesystem. "Volume" can be used in place of the term "drive" where it is desirable to indicate that the entity in question is not a physical disk drive, but rather the corporate data stored by using a filesystem there. "Logical drive" and "volume" should be considered synonymous, however "volume" and "partition" are not synonymous. In Linux systems, volumes are usually handled by the Logical Volume Manager or the Enterprise Volume Management System and manipulated using mount. See [| Wikipedia entry]

W

Walrus: A Eucalyptus component that allows users to store persistent data, organized as buckets and objects. You can use Walrus to create, delete, and list buckets, or to put, get, and delete objects, or to set access control policies. Walrus is interface compatible with Amazon’s Simple Storage Service (S3), providing a mechanism for storing and accessing virtual machine images and user data. Walrus can be accessed by end-users, whether the user is running a client from outside the cloud or from a virtual machine instance running inside the cloud. See [| Eucalyptus Installation Guide]

X

Xen Hypervisor: A virtual-machine monitor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently. The University of Cambridge Computer Laboratory developed the first versions of Xen. Since 2010, the Xen community develops and maintains Xen as free software, licensed under the GNU General Public License (GPLv2). Xen is available for the IA-32, x86-64, Itanium and ARM computer architectures. See [| Wikipedia entry]

Y

Z