Abstract: Reducing buffer space that is reserved when a VM attempts to write to disk. A shared memory maintains stored information available to all VM's, allowing translation between accessible to RSD's, independent of how that VM's storage is divided into VSD's. When a guest OS writes to a VSD, an “extent”, designating a location in the shared memory and amount of data to be transferred, which can be passed directly from the guest OS, through each element involved in translating the operation into one or more operations on RSD's, keeping copying to a minimum. No substantial changes need be made to the guest OS.

Abstract: Providing differing degrees of reliability or security for distinct devices within a reliable distributed system. Allowing virtual machines to operate in a reliable distributed system without either exposing the actual available devices to guest operating systems, or requiring the guest OS to maintain, or to maintain information about, reliability or security. Methods are responsive to a hierarchy of possible reliability or security failures, to guard more carefully against simultaneous failures of reliability or breaches of security, without additional work or delay. Functions invoked by the user that relate to reliability and security are hidden, so the user can specify a degree of reliability or security without having to implement those requirements themselves. Providing a uniform set of resources available to all users, separating out those individual resources that are allocated to particular users, and emulating particular devices at the request of those particular users.

Abstract: Reducing buffer space that is reserved when a VM attempts to write to disk. A shared memory maintains stored information available to all VM's, allowing translation between accessible to RSD's, independent of how that VM's storage is divided into VSD's. When a guest OS writes to a VSD, an “extent”, designating a location in the shared memory and amount of data to be transferred, which can be passed directly from the guest OS, through each element involved in translating the operation into one or more operations on RSD's, keeping copying to a minimum. No substantial changes need be made to the guest OS.

Abstract: Presenting information to operators of a cluster of physical devices, regarding resources being used by physical machines assigned to physical devices in those clusters. An operator console, coupled to the cluster of physical devices, receives information from those physical devices with respect to use of resources by virtual machines assigned to those physical devices. Each physical device reports virtual machines assigned thereto, and an physical memory assigned to each one. The operator console presents information to the operator regarding use of resources by virtual machines, in a natural and visible way. Physical devices are disposed horizontally to indicate a selected device, and vertically to indicate allocated resources. Virtual machines are disposed with each virtual machine occupying a vertical amount proportional to allocated resources. The graphical interface allows the operator to reallocate virtual machines to physical devices, or reallocate resources to virtual machines.

Abstract: Managing resources in a VM cluster; allocation of resources among competing VMs. Assigning VMs to real devices, responsive to needs for resources: processor usage, disk I/O, network I/O, memory space, disk space. Assigning VMs responsive to needs for cluster activity: network response latency, QoS. Using predictive models of resource usage by VMs. Transferring VMs, improving utilization. Failing-soft onto alternative VM resources. Providing a resource buffer for collective VM resource demand. Transferring VMs to a cloud service that charges for resources.

Abstract: Maintaining consistency and freshness of information about an operational system, assuring consistent actions by system actors, assuring that system elements use only a single global status of the system for any particular status time, assuring that each pair of elements acts only upon consistent status values, assuring that system elements operate only with status values measured sufficiently recently to be reliable. Information collectors respond to status values. Information containers respond to information collectors, maintaining status values and metadata indicating whether those status values are reliable, or are consistent with respect to known correct values. Information conditions respond to information collectors or information containers, maintaining logical consistency with a unified global status. System actors respond to information containers or information conditions, acting logically consistent with that global status.