Advanced Computer Architecture - Lecture 41: Networks and clusters

Advanced Computer Architecture - Lecture 41: Networks and clusters. This lecture will cover the following: a simple network; network topology; internetworking; omega interconnection topology; distributed switch topologies; ring network; multistage interconnection topology; crossbar switch topology;...

CS 704 Advanced Computer Architecture Lecture 41 Networks and Clusters (Networks: Interconnection and Topology ) Prof Dr M Ashraf Chughtai Today’s Topics Recap: A Simple Network Network Topology Internetworking Summary MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: I/O Systems and Storages Last time we concluded our discussion on the storage I/Os and communication I/Os Here, we noticed that the dependability, reliability, availability of the storage I/Os mostly influence the overall performance of computer systems Dependability is the quality of delivered service such that confidence can be placed on this service; and measured by quantifying the transitions between service accomplishment and service interruption MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: Dependability, reliability and Availability The dependability is measured in terms of the reliability and availability of a module The reliability of a module is the measure of the continuous service accomplishment or the measure of the time to failure, from a reference initial instant The availability of a module is the measure of the service accomplishment with respect to the swinging between the accomplishment and interruption states MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: I/O and Storage Systems The storages are interfaced with the processor using channel and backplane and network interconnects The networks are capable of sustaining high bandwidth transfer and their file-server operating system supports remote file access Hence, the network attached storages have very high dependability, but are more vulnerable to the reliability, so to improve the availability and performance of network …… MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: Network Attached Storages … attached storage system, disk arrays are introduced Here, the data is stripped across a set of disks which makes the collection appears to the software as a single large disk The throughput of disk arrays is improved due many small disk drives having high bandwidth The drawback to an array with more devices is that dependability of the device increases, hence, the reliability decreases; as generally N devices have 1/N reliability MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: Redundant Arrays of Disks The dependability of disk array is improved by adding redundant disks to the array to tolerate faults Such a disk array is called Redundant Array of Inexpensive Disk – RAID There exist several different approaches to include redundant disks in the disk array These approaches are usually classified by numerical value which identifies the RAID level MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: Redundant Arrays of Disks RAID is the disk array without any redundant disk, but employs the stripping of data across a set of disks RAID or disk Mirror array is one where each disk is fully duplicated onto its "shadow“ RAID or Bit-Interleaved Parity Disk employs a parity disk for each group of data; the parity computed across recovery group to protect against hard disk failures MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: Redundant Arrays of Disks RAID or Block Interleaved Parity and the RAID or Block Interleaved Distributed Parity, both use the same ratio of data disk to parity disk as RAID 3, but they access data differently In RAID level, the parity disk is associated to each data block, identical to it is associated to each data group in RAID 3, so it supports a mixture of both the small and large reads and writes MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) Recap: Redundant Arrays of Disks In RAID level, the parity disk is associated to each data block The data blocks are distributed among different disks in each row; i.e., the stripped data units are not located in the same disk This allows simultaneous read and write of more than one block MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 10 Crossbar Switch Topology A crossbar switch is a non-blocking switch that facilitate unidirectional interconnection of all the inputs (any processor) to any output to the other processor The interconnection of 2x2 crossbar switch are shown here [Fig 8.13 c] As you can see that nodes A, B can pass information equally to outputs C and D i.e., here no connections block any connection between other processor or memory units MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 43 Crossbar Switch Topology The organization of a crossbar topology for 8nodes (processors) is shown here [Fig 8.13 a] Note that a crossbar uses n2 switches where n is the number of processors Here, the links are unidirectional, i.e., the data comes in at one (left) link and goes out at other (right) link MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 44 Crossbar Switch Topology The routing depends on the style of addressing In source-based routing where message specifies the path to the destination, the message includes the sequence of out-bound arcs to teach the destination Thus, once an outgoing link (arc) is picked, the portion of the routing sequence is dropped from the packet MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 45 Crossbar Switch Topology In destination-based routing the message simply contains the destination address; and a program running in the switch decides from routing table which port to take for a given address A crossbar switch offers low latency and high throughput MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 46 Multistage Interconnection Topology An intermediate class of networks which lies between crossbar and bus based networks – Performance: more scalable than bus – Cost: more scalable than crossbar Built from small (e.g., 2x2 crossbar) switch nodes, with a regular interconnection pattern MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 47 Multistage Interconnection Topology The Omega Topology, depicted here Is a typical implementation of Multistage Topology Fig 8.13 b Here each switch is a 2x2 crossbar It has log2 n identical stages Here, the switches used are n/2 log2 n verses n2 in crossbar MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 48 Omega Interconnection Topology Here, the connection occur between the messages and depend on the pattern of communication and may give rise to blocking For example, for the Omega network shown, a message from P1 to P7 blocks while waiting for a message from P0 to P6 as has to follow the same path Repeat Fig 8.13 b highlighting the paths MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 49 Fully Connected Switching Network So far we have been discussing centralized switching topologies The distributed switching network is one where the switching is distributed throughout the network An ideal situation may be when the distributed switching allows to interconnect all nodes to A each other, as shown here Such a network is called Fully connected network MAC/VU-Advanced Computer Architecture C B D Lecture 41 Networks and Clusters (1) 50 Terminology of Distributed Network MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 51 Distributed Switch Topologies The simplest possible, low cost alternative to the fully interconnected network topology, is a distributed switch ring network, shown here Fig 8.15 As shown, a small switch is placed at every computer connected to the ring Here, as only two node are connected to a particular node, therefore the message will have to hop along intermediate node until the arrive at the final destination MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 52 Ring Network For example, where the 1st node is to connect to the 4th node, it hops the 2nd and 3rd nodes A variation to the Ring Network, to simplify the arbitration, is the Token Ring Here, a single slot (token) goes around the ring to determine which node is allowed to send the message – a node can send a message it gets a token MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 53 Ring Network The ring network has the following measure  Degree:  Diameter : N/2  Bisect:  Bandwidth = N  Latency = N/2 MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 54 Ring Network For example, where the 1st node is to connect to the 4th node, it hops the 2nd and 3rd nodes A variation to the Ring Network, to simplify the arbitration, is the Token Ring Here, a single slot (token) goes around the ring to determine which node is allowed to send the message – a node can send a message it gets a token MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 55 2D Grid and 2D Torus Mesh Connecting the switches associated with each node to the switches on the left and right and up and down and also connecting the switches to the of the top and bottom rows gives a grid structure Also connecting the switches of left and right columns give 2D Torus Mesh MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 56 Thanks and Allah Hafiz MAC/VU-Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 57 ... network MAC/VU -Advanced Computer Architecture C B D Lecture 41 Networks and Clusters (1) 50 Terminology of Distributed Network MAC/VU -Advanced Computer Architecture Lecture 41 Networks and Clusters. .. single computer In order to discuss the complexities and … MAC/VU -Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 16 Networks Communication Model … performance of networks, ... Interconnection Network MAC/VU -Advanced Computer Architecture Lecture 41 Networks and Clusters (1) 12 Interconnection Networks The standard components of a computer network are: – Computer nodes (also