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Single System Image
Transcript of Single System Image
7th C.E. Rollno.-52
Single I/O space
The need and use of :
What to do?
Single process space
Single System Boundaries
A middle-ware layer glues together all operating systems on all nodes offering a unified access to system resources.
Spend on M&S
Year 1 cost of sales!
Single System Image
A single system image (SSI) is the property of a system
that hides the heterogeneous and distributed nature of the
available resources and presents them to users and applications as a single unified computing resource
SSI is the illusion created by hardware or software that presents the collection of resources as one more powerful resource.
System Availability Infrastructure
Glues operating system on all nodes to offer unified access to system resources.
Enables cluster services like checkpointing,recovery from failure,fault tolerant support etc
• It provides a simple, straightforward view of all system resources and activities from any node in the cluster.
• It frees the end user from having to know where in the cluster an application will run.
• It allows the use of resources in a transparent way irrespective of their physical location.
• It lets the user work with familiar interface and commands and allows the administrator to manage the entire cluster as a single entity.
• It offers the same command syntax as in other systems and thus reduces the risk of operator errors, with the result that end users see improved performance, reliability, and higher availability of the system.
• It allows one to centralize/decentralize system management and control to avoid the need of skilled administrators for system administration.
• It greatly simplifies system management and thus reduced cost of ownership.
• It provides location independent message communication.
• It benefits the system programmers to reduce the time,effort, and knowledge required to perform the task and allows current staff to handle larger or more complex systems.
• It promotes the development of standard tools and utilities.
SSI Layers /Levels
• operating system,
1. Every SSI has a boundary.
2. SSI support can exist at different levels within a
system—one able to be built on another.
This allows any node to perform I/O operations on local or remotely located peripheral or disk devices. In this SIOS design, disks associated to cluster nodes, network-attached RAIDs, and
peripheral devices form a single address space.
-All user processes, no matter on which nodes they reside, have a unique cluster-wide process ID.
-A process on any node can create child processes on the same or different node.
-A process should also be able to communicate with any other process on a remote node. Clusters should support globalized process management and allow the management and control of processes as if they are running on local machines
Checkpointing and process migration
Checkpointing is a software mechanism to periodically save the process state and intermediate computing results in memory or disks.
This allows the rollback recovery after a
failure. Process migration is needed in dynamic load balancing among the cluster nodes and in supporting checkpointing.
Single entry point
Single virtual networking
Single control point and management
Single memory space
Single job management system
Single user interface
A user can connect to the cluster as a virtual host, although the cluster may have multiple physical host nodes to serve the login session. The system transparently distributes the user’s connection requests to different physical hosts to balance the load.
On entering into the system, the user sees a single, huge file system image as a single hierarchy of files and directories under the same root directory that transparently integrates local and global disks and other file devices.
The entire cluster and each individual node can be configured, monitored, tested, and controlled from a single window using single GUI tools, much like an NT workstation managed by the task manager tool.
This means that any node can access any network connection throughout the cluster domain even if the network is not physically connected to all nodes in the cluster. Multiple networks support a single virtual network operation
Users have an illusion of a big,centralized main memory, which in reality may be a set of distributed local memories. Software DSM approach has already been used to achieve single memory space on clusters. Another approach is to let the compiler distribute the data structure of an application across multiple nodes. It is still a challenging task to develop a single
memory scheme that is efficient, platform independent,and able to support sequential binary codes.
Under a global job scheduler, a user job can be submitted from any node to request any number of host nodes to execute it. Jobs can be scheduled to run in either batch, interactive, or parallel modes.
The user should be able to use the cluster through a single GUI. The interface must
have the same look and feel as the one available for workstations