Definitions

Hypervisor products may contain terms with which you are unfamiliar. This section defines some of the more common terms, as well as terms specific to Pervasive PSQL Vx Server. It is to these definitions Pervasive PSQL Vx Server refers if the term is used in the Pervasive PSQL documentation.

Table 4

Terms Pertaining to Hypervisor Products and to Pervasive PSQL Vx Server

A physical machine running a hypervisor that hosts VMs.

Clone operation

A procedure that produces a VM with the same MAC addresses and system ID (SID) as the original.

A duplicate of a virtual machine. A full clone is a complete copy of the original virtual machine, including all associated virtual disks. A linked clone is a copy of the original virtual machine. The copy must have access to the parent virtual machine’s virtual disks. A linked clone stores changes to the virtual disks in a separate set of files.

A tool for converting a physical machine image to a VM, or one VM format to another VM format. By default, a converted VM has a different MAC address, IP address, and system identifier (SID), but you can edit these properties on-the-fly during the conversion.

A VM is considered copied if it is modified as it is copied. The result is two differing VMs after copying.

A procedure that produces a VM with a different MAC address(es) and system ID (SID) from the original.

Distributed Power Management (DPM) is a feature offered by VMware, Inc. that saves power by dynamically right-sizing DRS cluster capacity according to workload demands. See also DRS.

Distributed Resource Scheduler (DRS) is a feature offered by VMware, Inc. that dynamically balances computing capacity across a collection of hardware resources aggregated into logical resource pools. DRS automatically allocates additional resources by redistributing virtual machines among the physical servers in the resource pool. See Resource Pool.

An enterprise-level computer virtualization product offered by VMware, Inc. that runs directly on server hardware without requiring an additional underlying operating system.

Enhanced vMotion Compatibility (EVC) is a feature from VMware, Inc. that allows you to migrate VMs between different generations of CPUs.

Fiber Channel over Ethernet (FCoE) is the standard for using Fiber Channel protocol over Ethernet networks.

Fault Tolerance (FT) is the ability of a system to respond gracefully to an unexpected hardware or software failure. The lowest level of fault tolerance is the ability to continue operation in the event of a power failure. Many fault-tolerant computer systems mirror all operations in which every operation is performed on two or more duplicate systems, so if one fails the other can take over.

Fault Tolerance/High Availability. See FT and HA.

Full Virtualization

A type of virtualization in which the virtual machine simulates enough hardware to allow an unmodified guest operating system to be run in isolation.

The operating system that runs in a virtual machine. There can be multiple guests per hypervisor, but only one per virtual machine. See also Host.

High Availability (HA) refers to the availability of resources in a computer system in the wake of component failures in the system. 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.

Hardware-assisted Virtualization

A type of virtualization in which the hardware provides architectural support that facilitates building a virtual machine monitor and allows guest operating systems to be run in isolation. The most powerful form of virtualization since the hardware contributes in significant ways to improve the virtualization effort.

Host Bus Adapter (HBA) is an I/O adapter that sits between the host computer's bus and the Fiber Channel loop and manages the transfer of information between the two channels. In order to minimize the impact on host processor performance, the host bus adapter performs many low-level interface functions automatically or with minimal processor involvement.

A computer that uses virtualization software to run virtual machines. Also called the host machine or host computer. The physical computer on which the virtualization software is installed.

A platform that allows multiple operating systems to run on a host computer at the same time.

A state in which a VM remains executing, but not actively online or performing real work. See also vLockStep.

The Microsoft term for moving the execution of the VM to a different appliance while the VM is still running without a dropped network connection or perceived downtime.

Media access control (MAC) is a hardware address that uniquely identifies each node of a network.

A action that involves moving the files that make up a VM from one location to another resulting in only one instance of the VM after the movement. Contrast with Clone.

Open Virtualization Format (OVF) is a packaging standard designed to address the portability and deployment of virtual appliances. Independent software vendors (ISVs) can use OVF to create a single, pre-packaged appliance that can run on customers’ virtualization platforms of choice. See also The Distributed Management Task Force, Virtualization Management at http://dmtf.org/standards/vman.

Paravirtualization

A type of virtualization in which the virtual machine does not necessarily simulate hardware, but instead, or in addition, offers a special API with which the guest operating system can makes special hyper-calls that ask the hypervisor to behave in non-traditional ways. For example, a paravirtualized environment can pretend to be running on completely different hardware than is actually available.

Partial Virtualization

A type of virtualization in which some but not all of the target environment is simulated. Usually, this means that entire operating systems cannot run in the virtual machine—which would be full virtualization—but that many applications can run. If certain hardware features of the target environment are not simulated, then any applications using those features will fail.

Physical Pervasive PSQL Vx Server

An instance of Pervasive PSQL Vx Server on a physical machine. See also Pervasive PSQL Vx Server Instance.

A logical grouping for access control, organization, and restriction of VMs. The VMs are already loaded, configured and authenticated; they’re simply idle/suspended. Nothing about the VM is changed when it is started from a pool except possibly the appliance that is hosting it.

Pervasive PSQL Vx Server Instance

An installed Pervasive PSQL Vx Server on a physical or a virtual machine.

Quick Migration

The Microsoft term for suspending a VM, assigning it to a different appliance, then resuming the VM. Any connections to this VM are dropped.

A logical abstraction for flexible management of resources (“resources” include CPU, memory, power, storage, and network resources).

A backup copy of selectable portions of data within storage arrays.

Site Recovery Manager (SRM) is a product from VMware, Inc. for disaster recovery that provides centralized management of recovery plans, enables non-disruptive testing, and automates site recovery and migration processes.

Storage vMotion

A product from VMware, Inc. that enables live migration of VM disk files across storage arrays (storage migration) with no interruption in service for critical applications.

Suspended state

A VM state in which the operating system and any running applications are halted in mid-execution so the data can be written to a suspend-state file.The suspended VM can be later resumed with all applications and data exactly where they were before the suspended state was initiated. A suspended state is very similar to the hibernate functionality provided by various operating systems.

A VM template provides a standardized group of hardware and software settings that can be used repeatedly to create new VMs configured with those settings. A new VM created from a template typically produces a different MAC address and system identifier (SID). Other configuration and software properties remain identical to the template’s source VM unless you modify the properties during the template startup and creation of the new VM.

Some hypervisor products also allow you to specify a run-once script to be invoked to handle any per-VM customizations. It is with a run-once script that you could invoke the Pervasive PSQL Vx Server clilcadm utility to authorize a key, for example.

A product from Hitachi Data Systems that provides continuous, nondisruptive, host-independent remote data replication for disaster recovery or data migration over any distance.

Universal Converged Network Adapter (UCNA) is a high-performance Ethernet (10GbE) multi-function adapter from Emulex that provides optimized network and storage performance with protocol offloads for TCP/IP, TCP Offload Engine (TOE), Fiber Channel over Ethernet (FCoE) and iSCSI.

Universal Storage Platform (USP) is the brand name for a Hitachi Data Systems line of enterprise storage arrays.

The technology behind VMware, Inc. Fault Tolerance that keeps two VMs synchronized.

Virtual Machine (VM). A software implementation of a machine (a computer) that executes programs like a physical machine.

A feature from VMware, Inc. that enables the live migration of running VMs from one physical server to another with zero downtime, continuous service availability, and complete transaction integrity.

A feature of the XenServer product from Citrix that allows live migration of running VMs from one physical host system to another without any disruption or downtime.