Scale Computing

Other

Philip R White

Scott Loughmiller

Nate Hardt

Michael McLaughlin

Reliably testing distributed systems in which multiple components interact, including: provisioning resources by a test leader, directing components to perform actions required by test suites, and reporting results. Provisioning resources might be batched in advance, and might overlap resources for multiple test suites. Provisioning and directing might occur on an as-needed basis, might be performed concurrently, and might be reordered for relatively better performance. Directing actions might occur on command by test leaders, might occur by synchronization of resources, or might occur by resources requesting permission to proceed. Resources might act only upon direction by test leaders, or might act on their own initiative when synchronized. Results might be reported to the test leader for comparison, maintained in a database for access by the test leader, or compared by resources on their own initiative in response to instructions from the test leader.

Distributed test suite tools

In a reliable distributed computing system, techniques where user actions or events affecting real system devices (RSD's), or causing the system to make changes to metadata, require fewer accesses to RSD's. When a virtual system device (VSD) is mounted, substantially all the metadata, or at least that associated with data recovery, is read into memory. Changes to that metadata can be made substantially without any metadata accesses to RSD's. No metadata accesses to RSD's are made for read operations, as the RSD would remain unchanged. Metadata is flushed from memory upon write operations. Metadata about data locations can be maintained in memory, so as to be available if any RSD becomes corrupted or otherwise comes to lose data.

Metadata caches in a reliable distributed computing system

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. Users do not have access to 'real' devices the distributed system can use, only 'virtual' devices presented by the distributed system, where those virtual devices have properties similar, but not necessarily equal, to real devices.

Virtual devices in a reliable distributed computing system

Techniques that can minimize latency during remote access between nodes in a reliable distributed computing system. A local computing device includes a protocol data unit that interacts with a substantially similar unit at a remote computing device. Each unit executes a finite state machine that is designed to minimize both the amount of wait time between messages and the number of round-trip message exchanges. The state machine resolves each request as quickly as possible to one of three states: SUCCESS, in which the transfer is successful and it is feasible to free the data transfer buffer, COMPLETE, in which the transfer is finished and a next transfer can be initiated, ABORT, in which either the sending or receiving unit declares the transfer to have failed (or aborted by a higher level element).

Remote access latency in a reliable distributed computing system

Reliably making configuration changes to distributed systems, including receiving commands for multiple configuration changes, subdividing configuration changes into separate tasks, and performing those tasks at each node. A configuration element receives sets of configuration change commands, acknowledging them so the user need not wait before issuing additional commands. Tasks are determined, each including consistent changes to system configuration, and each including single-device tasklets. Each particular tasklet might be assigned to a particular single device, or to any single device in the system. Next tasks are performed when tasklets are complete. If tasklets are not timely performed due to nodes which are relatively unresponsive, those nodes are marked 'failed.' When a failed node returns to responsiveness, it marks itself 'recovering.' When a recovering node catches up, it marks itself &#x201c;operational.&#x201d; Updates by failed or recovering nodes are skipped while synchronizing with operational nodes.

Distributed dynamic system configuration

Real system devices (RSD's) emulate virtual system devices (VSD's); system elements can use RSD's and manipulate VSD's, while users can only use VSD's. Identifying when RSD's have erroneous data. Providing a mapping of RSD's to VSD's, to recover a maximum set of VSD's. Providing a mapping of VSD's to RSD's, to recover a specified most valuable VSD. Reconstructing VSD's from RSD's having erroneous data, and coordinating with a user's assistance to couple RSD's in an order allowing data recovery. Metadata is maintained coupling data identifiable on VSD's with corresponding data on RSD's; it is possible to trace connections between RSD's and VSD's even without complete data.

Recovery after data loss in a reliable distributed computing system

Techniques for distributing tests and test suites across a network

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. System actors might include those which notify monitors or operators, and those which modify the system to detect and correct operation gone awry.

Condition detection and reporting in complex systems

A swing motion device for providing exercise and training has a plurality of collapsible vanes mounted on a shaft that an athlete may grip and swing through the air. The vanes provide air resistance against which the athlete's muscles must work. Each vane may comprise a foldable wire framework covered with a bag-like fabric sheath. When the vanes are collapsed, the device assumes a compact shape that facilitates transport and storage.

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San Diego, CA, United States of America

Philip R White