Scalability .

• Scalability

https://store.theartofservice.com/the-scalability-toolkit.html

Border Gateway Protocol Internal BGP scalability

1 An autonomous system with internal BGP (iBGP) must have all of its iBGP peers

connect to each other in a full mesh (where everyone speaks to everyone directly). This full-mesh configuration requires that each router maintain a session to every other router. In large networks, this number of sessions may degrade performance of

routers, due to either a lack of memory, or too much CPU process requirements.



1 Route reflectors and confederations both reduce the number of iBGP

peers to each router and thus reduce processing overhead. Route

reflectors are a pure performance-enhancing technique, while

confederations also can be used to implement more fine-grained policy.



1 Route reflectors reduce the number of connections required in an AS. A

single router (or two for redundancy) can be made a route reflector: other

routers in the AS need only be configured as peers to them.



1 Confederations are sets of autonomous systems. In common

practice, only one of the confederation AS numbers is seen by

the Internet as a whole. Confederations are used in very large

networks where a large AS can be configured to encompass smaller more manageable internal ASs.



1 Confederations can be used in conjunction with route reflectors.

Both confederations and route reflectors can be subject to

persistent oscillation unless specific design rules, affecting both BGP and

the interior routing protocol, are followed.



1 However, these alternatives can introduce problems of their own, including the following:



1 route oscillation



1 Additionally, route reflectors and BGP confederations were not designed to

ease BGP router configuration. Nevertheless, these are common

tools for experienced BGP network architects. These tools may be combined, for example, as a hierarchy of route reflectors.


Scalability

1 An analogous meaning is implied when the word is used in an

economic context, where scalability of a company implies that the

underlying business model offers the potential for economic growth within

the company.


Scalability

1 Scalability, as a property of systems, is generally difficult to define and in any

particular case it is necessary to define the specific requirements for scalability on those dimensions that are deemed important. It is

a highly significant issue in electronics systems, databases, routers, and

networking. A system whose performance improves after adding hardware,

proportionally to the capacity added, is said to be a scalable system.


Scalability

1 Scalability refers to the ability of a site to increase in size as demand warrants.


Scalability

1 The concept of scalability is desirable in technology as well as business settings. The base concept is consistent – the ability for a business or technology to accept increased volume without impacting the contribution margin (= revenue − variable costs). For example, a given piece of equipment may

have capacity from 1–1000 users, and beyond 1000 users, additional equipment is needed

or performance will decline (variable costs will increase and reduce contribution margin).


Scalability Measures

1 Scalability can be measured in various dimensions, such as:



1 Administrative scalability: The ability for an increasing number of

organizations or users to easily share a single distributed system.



1 Functional scalability: The ability to enhance the system by adding new

functionality at minimal effort.



1 Geographic scalability: The ability to maintain performance, usefulness, or

usability regardless of expansion from concentration in a local area to

a more distributed geographic pattern.



1 Load scalability: The ability for a distributed system to easily expand

and contract its resource pool to accommodate heavier or lighter

loads or number of inputs. Alternatively, the ease with which a

system or component can be modified, added, or removed, to

accommodate changing load.


Scalability Examples

1 A routing protocol is considered scalable with respect to network size,

if the size of the necessary routing table on each node grows as O(log N), where N is the number of nodes

in the network.



1 A scalable online transaction processing system or database

management system is one that can be upgraded to process more transactions by adding new

processors, devices and storage, and which can be upgraded easily and transparently without shutting it

down.



1 Some early peer-to-peer (P2P)

implementations of Gnutella had scaling

issueshttps://store.theartofservice.com/the-scalability-toolkit.html


1 The distributed nature of the Domain Name System allows it to work

efficiently even when all hosts on the worldwide Internet are served, so it is

said to "scale well".


Scalability Horizontal and vertical scaling

1 Methods of adding more resources for a particular application fall into

two broad categories: horizontal and vertical scaling.



1 To scale horizontally (or scale out) means to add more nodes to a system, such as adding a new

computer to a distributed software application



1 To scale vertically (or scale up) means to add resources to a single

node in a system, typically involving the addition of CPUs or memory to a

single computer



1 There are tradeoffs between the two models


Scalability Database scalability

1 A number of different approaches enable databases to grow to very large size while

supporting an ever-increasing rate of transactions per second. Not to be

discounted, of course, is the rapid pace of hardware advances in both the speed and

capacity of mass storage devices, as well as similar advances in CPU and networking

speed. Beyond that, a variety of architectures are employed in the implementation of very

large-scale databases.



1 One technique supported by most of the major database management

system (DBMS) products is the partitioning of large tables, based on

ranges of values in a key field



1 Oracle RAC uses a different model to achieve scalability, based on a

"shared-everything" architecture that relies upon high-speed connections

between servers.



1 In any case, whether or not adhering to traditional relational concepts,

there appears to be no limit in sight to database scalability.


Scalability Design for scalability

1 It is often advised to focus system design on hardware scalability rather than on capacity


Scalability Weak versus strong scaling

1 In the context of high performance computing there are two common notions of scalability.



1 The first is strong scaling, which is defined as how the solution time

varies with the number of processors for a fixed total problem size.



1 The second is weak scaling, which is defined as how the solution time

varies with the number of processors for a fixed problem size per

processor.


Linux Terminal Server Project - Scalability

1 Initially, the MILLE-Xterm project, funded by Canadian public agencies and school

districts in the province of Quebec, created a version of LTSP integrating four

subprojects: a portal (based on uportal), an open-source middleware stack, a CD with

free software for Windows/Mac and, finally, MILLE-Xterm itself. The MILLE-Xterm

project's goal was to provide a scalable infrastructure for massive X-Terminal

deployment.https://store.theartofservice.com/the-scalability-toolkit.html


1 MILLE means Modèle d'Infrastructure Logiciel Libre en Éducation (Free Software Infrastructure Model for

Education) and is targeted at educational institutions.



1 As of 2009, MILLE-Xterm was integrated back into the LTSP as

LTSP-cluster, a project specializing in the large scale deployment of LTSP



1 In LTSP-cluster high-availability and high-performance thin-clients are

specified through the optional use of redundant components. Services that

can be load-balanced and made highly available are:



1 LTSP-Cluster can support Linux application servers as well as

Windows application servers and provides a similar level of support,

centralized management, high-availability, and load-balancing

features for both platforms.



1 Also included is support for virtual desktops for remote users using NX

technology. The NX protocol can allow remote Windows and Linux sessions to be accessed from a web browser with

very low bandwidth (40 kbit/s) requirements and tolerance for high-

latency connections. The NX client runs on various Operating Systems including

Linux, Mac, and Windows.


Storage virtualization - Performance and scalability

1 In some implementations the performance of the physical storage

can actually be improved, mainly due to caching



1 Due to the nature of virtualization, the mapping of logical to physical

requires some processing power and lookup tables. Therefore every

implementation will add some small amount of latency.



1 In addition to response time concerns, throughput has to be

considered. The bandwidth into and out of the meta-data lookup software directly impacts the available system

bandwidth. In asymmetric implementations, where the meta-

data lookup occurs before the information is read or written,

bandwidth is less of a concern as the meta-data are a tiny fraction of the actual I/O size. In-band, symmetric flow through designs are directly limited by their processing power

and connectivity bandwidths.



1 Most implementations provide some form of scale-out model, where the inclusion of additional software or

device instances provides increased scalability and potentially increased

bandwidth. The performance and scalability characteristics are directly

influenced by the chosen implementation.


Virtual Private LAN Service - Scalability

1 VPLS is typically used to link a large number of sites together. Scalability is therefore an important issue that

needs addressing.


PRINCE2 - Scalability

1 For this reason every process has a note on scalability


Extreme programming - Scalability

1 Historically, XP only works on teams of twelve or fewer people. One way to circumvent this limitation is to break up the project into smaller pieces and the team into smaller

groups. It has been claimed that XP has been used successfully on teams

of over a hundred developers. ThoughtWorks has claimed

reasonable success on distributed XP projects with up to sixty people.


Extreme programming - Scalability

1 In 2004, Industrial Extreme Programming (IXP) was introduced as

an evolution of XP. It is intended to bring the ability to work in large and

distributed teams. It now has 23 practices and flexible values. As it is a new member of the Agile family,

there is not enough data to prove its usability; however it claims to be an

answer to what it sees as XP's imperfections.


Scalability testing

1 Scalability Testing, part of the battery of non-functional tests, is the testing

of a software application for measuring its capability to scale up or scale out - in terms of any of its non-functional capability - be it the user load supported, the number of transactions, the data volume etc.


Scalability testing

1 Performance, scalability and reliability are usually considered

together by software quality analysts.


Scalability testing - Tools

1 Scalability testing tools exist (often leveraging scalable resources

themselves) in order to test load, concurrent connections, transactions,

and throughput of many internet services. Of the available testing

services, those offering API support suggest that environment of continuous deployment also continuously test how recent

changes may impact scalability.https://store.theartofservice.com/the-scalability-toolkit.html

Scalability testing - Tools

1 SandStorm Cloud Edition


Scalability testing - Further reading

1 Designing Distributed Applications with Visual Studio .NET: Scalability


Google Search Appliance - Scalability

1 * Multiple appliances can be linked together to scale to billions of documents.


Google Search Appliance - Scalability

1 * Physical hardware can be distributed

across multiple locations.


Mobile banking - Scalability and reliability

1 Another challenge for the chief information officer|CIOs and chief

technical officer|CTOs of the banks is to scale-up the mobile banking

infrastructure to handle exponential growth of the customer base


Ultra Density Optical - High capacity and scalability

1 Blue laser technology gives the 30 GB UDO more than three times the capacity of

previous generation MO (Magneto Optical) and DVD technologies. Being removable, UDO cartridges, combined with off-line

media management capabilities typical of optical storage libraries, makes UDO a much more scalable format. Rarely used data can

be removed from a library, freeing up capacity yet remaining managed and

accessible.https://store.theartofservice.com/the-scalability-toolkit.html

Scalable - Database scalability

1 A number of different approaches enable databases to grow to very

large size while supporting an ever-increasing rate of Transactions Per

Second|transactions per second. Not to be discounted, of course, is the

rapid pace of hardware advances in both the speed and capacity of mass

storage devices, as well as similar advances in CPU and networking

speed.https://store.theartofservice.com/the-scalability-toolkit.html


1 One technique supported by most of the major Database management

system|database management system (DBMS) products is the

Partition (database)|partitioning of large tables, based on ranges of

values in a key field



1 Oracle RAC uses a different model to achieve scalability, based on a

shared-everything architecture that relies upon high-speed connections

between servers.


Scalable - Performance tuning versus hardware scalability

1 It is often advised to focus system design on hardware scalability rather than on capacity


Information and communication technologies for development - Sustainability and scalability

1 Currently, the main two perspectives coming out of this sector are to

emphasize the need for external aid to build infrastructure so that

projects can reach viability, and the need to develop and build on local

talent.



1 Establishing a clear and effective initial design serves as a foundation

of any development projects



1 Sustaining the project's scalability is a huge challenge of ICT for

development; how the target user will continue using the platform



1 Also, a number of developing countries have proven their skills in IT (information technology). Using

these skills to build on ICT4D projects will tap local potential and a key

indigenous partner in the growth of this sector will be gained. The

balance of trade for these nations due to imports in both computer

hardware|hardware and computer software|software might be an

additional consideration.



1 Different countries have variety on these strengths some are better in hardware

production, both high end and low end. There are some who are good in production of

programs and other content. ICT is a US$ 3 trillion dollar industry

(2010)http://www.deltapartnersgroup.com/ict-in-emerging-markets-a-usd-200-bln-opportunity-

that-cannot-be-ignored and is growing every year. Communication, media and IT present

opportunities for further growth and expansion.


Xen - Scalability

1 Xen can scale to 4095 physical CPUs, 512 VCPUs per HVM guest, 256

VCPUs per PV guest, 16TB of RAM per host, and up to 1TB of RAM per HVM

guest or 512 GB of RAM per PV guest.


Real time control protocol - Scalability in large deployments

1 In large-scale applications, such as in Internet Protocol Television (IPTV),

very long delays (minutes to hours) between RTCP reports may occur, because of the RTCP bandwidth control mechanism required to

control congestion (see #Protocol functions)


Real time control protocol - Scalability in large deployments

1 [http://www.academypublisher.com/jnw/vol03/no03/jnw03030110.pdf Realtime control protocol and its

improvements for Internet Protocol Television]


Software asset management - Issues with scalability

1 An example of issues faced when scaling up discovery tools is with

Microsoft's System Centre Configuration Manager (SCCM).


Software asset management - Issues with scalability

1 Using metering rules to monitor software deployment and usage across a small

estate is relatively easy and reliable given the total number of unique executables

(.exe files) and the number of instances of each executable. If you try turning on

metering rules for every packaged application and every executable in a large

estate the volume of data generated quickly becomes unmanageable and expensive to

maintain.https://store.theartofservice.com/the-scalability-toolkit.html

Freenet - Scalability

1 As of now, the scalability of freenet has yet to be tested.


Computer icon - Size and scalability

1 The standard icon is generally the size of an adult thumb, enabling both easy visual recognition and use in a

touchscreen device


Nutch - Scalability

1 IBM Research studied the performance[http://www.cecs.uci.edu/~papers/ipdps07/pdfs/SMTPS-201-paper-1.pdf Scalability of the Nutch search engine] of Nutch/Lucene as part of its Commercial Scale Out

(CSO) project.[http://weather.ou.edu/~apw/

projects/cso/prov_paper.pdf Base Operating System Provisioning and

Bringup for a Commercial Supercomputer] Their findings were that a Horizontal scaling|scale-out

system, such as Nutch/Lucene, could achieve a performance level on a

cluster of blades that was not achievable on any Scalability#Scale

vertically (scale up)|scale-up computer such as the Power5.


Nutch - Scalability

1 The ClueWeb09 dataset (used in e.g. Text Retrieval Conference|TREC) was

gathered using Nutch, with an average speed of 755.31 documents

per second.[http://boston.lti.cs.cmu.edu/

crawler/crawlerstats.html The Sapphire Web Crawler - Crawl

Statistics]. Boston.lti.cs.cmu.edu (2008-10-01). Retrieved on 2013-07-

21.https://store.theartofservice.com/the-scalability-toolkit.html

BGP - Internal BGP scalability

1 An autonomous system with internal BGP (iBGP) must have all of its iBGP

peers connect to each other in a Complete graph|full mesh (where

everyone speaks to everyone directly). This full-mesh configuration requires that each router maintain a

session to every other router. In large networks, this number of sessions

may degrade performance of routers, due to either a lack of memory, or

too much CPU process requirements.



1 Route reflectors[http://www.ietf.org/rfc/rfc4

456.txt BGP Route Reflection: An Alternative to Full Mesh Internal BGP

(iBGP)], RFC 4456, T. Bates et al., April 2006 reduce the number of connections required in an AS. A

single router (or two for redundancy) can be made a route reflector: other

routers in the AS need only be configured as peers to them.



1 BGP confederation|Confederations are sets of autonomous systems. In

common practice,[http://www.ietf.org/rfc/rfc50

65.txt Autonomous System Confederations for BGP], RFC 5065, P. Traina et al., February 2001 only

one of the confederation AS numbers is seen by the Internet as a whole.

Confederations are used in very large networks where a large AS can be configured to encompass smaller more manageable internal ASs.



1 * route oscillation



1 * increase of BGP convergence time[http://www.ietf.org/rfc/rfc4098.t

xt Terminology for Benchmarking BGP Device Convergence in the

Control Plane], RFC 4098, H. Berkowitz et al., June 2005


NTFS - Scalability

1 In theory, the maximum NTFS volume size is 264−1 clusters


NTFS - Scalability

1 The maximum theoretical file size on NTFS is 16exabyte|EB () minus 1 kB

or 18,446,744,073,709,550,592 bytes. With Windows 8 and Windows Server 2012, the maximum file size implemented is 256 TB minus 64 KB

or 281,474,976,645,120 bytes.


NTFS - Scalability

1 NTFS supports a maximum cluster size of 64 kB.


Reconfigurable Manufacturing Systems - Scalability

1 the ability to easily change production capacity by rearranging an existing manufacturing system

and/or changing the production capacity of reconfigurable stations.


Reconfigurable Manufacturing Systems - Scalability

1 Scalability is the counterpart characteristic of convertibility. Scalability may require at the

machine level adding spindles to a machine to increase its productivity,

and at the system level changing part routing or adding machines to expand the overall system capacity (i.e., maximum possible volume) as

the marketfor the product grows.https://store.theartofservice.com/the-scalability-toolkit.html

Four square - Game scalability

1 Four square is a popular game for children and school playgrounds. It is possible to scale the game's difficulty

and supervision appropriately for different age groups and ability

levels. Schools, churches, and camps often change the size of the court, the type of ball, or aspects of the

rules to best suit the players' abilities.


Lossy data compression - Downsampling/compressed representation scalability

1 One may wish to downsample or otherwise decrease the resolution of the represented source signal and the quantity of data used for its

compressed representation without re-encoding, as in bitrate peeling, but this functionality is not supported in all designs, as not all codecs encode

data in a form that allows less important detail to simply be

dropped.https://store.theartofservice.com/the-scalability-toolkit.html


1 Some well known designs that have this capability include JPEG 2000 for still images and H.264/MPEG-4 AVC

based Scalable Video Coding for video. Such schemes have also been

standardized for older designs as well, such as JPEG images with

progressive encoding, and MPEG-2 and MPEG-4 Part 2 video, although

those prior schemes had limited success in terms of adoption into

real-world common usage.



1 Without this capacity, which is often the case in practice, to produce a

representation with lower resolution or lower fidelity than a given one,

one needs to start with the original source signal and encode, or start with a compressed representation

and then decompress and re-encode it (transcoding), though the latter tends to cause digital generation

loss.https://store.theartofservice.com/the-scalability-toolkit.html


1 Another approach is to encode the original signal at several different

bitrates, and their either choose which to use (as when streaming over the internet

– as in RealNetworks' SureStream – or offering varying downloads, as at Apple's iTunes Store), or broadcast several, where

the best that is successfully received is used, as in various implementations of

hierarchical modulation



1 Some audio formats feature a combination of a lossy format and a

lossless correction which when combined reproduce the original

signal; the correction can be stripped, leaving a smaller, lossily

compressed, file. Such formats include MPEG-4 SLS (Scalable to

Lossless), WavPack, and OptimFROG DualStream.


Extensible Host Controller Interface - Scalability

1 The xHCI architecture was designed to be highly scalable, capable of

supporting 1 to 255 USB devices and 1 to 255 root hub ports



1 The xHCI maintains queue state in system memory as Endpoint Context data structures



1 Also USB endpoint activity tends to be bursty. That is, at any point in time a large number of endpoints

may be ready to move data, however only a subset are actively moving data. For instance, the interrupt IN

endpoint of a mouse may not transfer data for hours if the user is away from their desk. xHCI vendor

specific algorithms could detect this condition and make that endpoint a

candidate for paging out if other endpoints become busy.



1 * The xHCI architecture allows large maximum values for the number of

USB devices, ports, interrupt vectors, etc. supported, however an

implementation only needs to define the number necessary to meet its

marketing requirements. For instance, a vendor could choose to

limit the number of USB devices that it supported for a tablet xHCI

implementation to 16 devices.https://store.theartofservice.com/the-scalability-toolkit.html


1 * A vendor can further take advantage of xHCI architectural features to scale its internal

resources to match its target usage models. For instance, if through usability testing a vendor determines that 95% of tablet users will never connect more than 4 USB devices, and each USB device typically defines 4 endpoints (or less), then internal caching for 16 Endpoint

Contexts will ensure that under normal conditions there will be no system memory

activity due to Endpoint Context paging.


Network on a chip - Parallelism and scalability

1 Therefore, as the complexity of Very-large-scale integration|integrated

systems keeps growing, a NoC provides enhanced performance

(such as throughput) and scalability in comparison with previous

communication architectures (e.g., dedicated point-to-point signal wires,

shared Computer bus|buses, or segmented Computer bus|buses with

bridges)https://store.theartofservice.com/the-scalability-toolkit.html

ICT for Development - Sustainability and scalability

1 Different countries have variety on these strengths some are better in hardware

production, both high end and low end. There are some who are good in production of

programs and other content. ICT is a US$3 trillion industry

(2010)http://www.deltapartnersgroup.com/ict-in-emerging-markets-a-usd-200-bln-opportunity-

that-cannot-be-ignored and is growing every year. Communication, media and IT present

opportunities for further growth and expansion.


Publish–subscribe - Scalability

1 However, in certain types of tightly coupled, high-volume enterprise

environments, as systems scale up to become data centers with thousands

of servers sharing the pub/sub infrastructure, current vendor

systems often lose this benefit; scalability for pub/sub products

under high load in these contexts is a research challenge.


Publish–subscribe - Scalability

1 : Outside of the enterprise environment, on the other hand, the pub/sub paradigm has proven its scalability to volumes far beyond those of a

single data centre, providing Internet-wide distributed messaging through web syndication

protocols such as RSS and Atom (standard). These syndication protocols accept higher latency and lack of delivery guarantees in

exchange for the ability for even a low-end web server to syndicate messages to (potentially)

millions of separate subscriber nodes.


Service-oriented architecture implementation framework - Fault tolerance, reliability and scalability

1 A SOAIF should be able to offer an extremely high degree of reliability. The platform should support a broad

range of processes that span an increasing number of applications,

corporations, and partners. To eliminate single points of failure and

to maximize performance, a fully distributed architecture becomes

essential. https://store.theartofservice.com/the-scalability-toolkit.html

Service-oriented architecture implementation framework - Fault tolerance, scalability and reliability

1 Several modern ESBs implement a symmetric, distributed architecture

in which peer-messaging servers run on multiple nodes of an enterprise

network, providing a highly scalable, reliable distributed messaging platform with no single point of

failure


Service-oriented architecture implementation framework - Fault tolerance, scalability and reliability

1 Ensuring that data flowing between services does not always have to

traverse a central point in the network optimizes peer-to-peer

network performance


Vowpal Wabbit - Scalability

1 Vowpal wabbit has been used to learn a tera-feature (1012) data-set

on 1000 nodes in one hour.http://arxiv.org/abs/1110.4198

Its scalability is aided by several factors:



1 * Out-of-core online learning: no need to load

all data into memory



1 * The Feature hashing|hashing trick: feature identities are converted to a weight index via a hash (uses 32-bit

MurmurHash3)



1 * Exploiting multi-core CPUs: parsing of input and learning are done in separate threads.


Trust metric - Scalability

1 The growing size of networks of trust make scalability another desired

property, meaning that it is computationally feasible to calculate

the metric for large networks. Scalability usually puts two requirements of the metric:



1 * The elementary operation (e.g. fusion or discount) is computationally

feasible, e.g. that relationships between context of trust can be

quickly established.



1 * The number of elementary operations scale slowly with the growth of the network.


Construction field computing - Scalability and continual change

1 Technologies will evolve and the user will be facing new challenges with each change. It is usually wiser to

adopt a small system that works and then later add features. This gradual

adoption reduces anxiety and increases acceptance and use. This

work by [http://www.usm.main.edu/com/linda

p~1.htm Linda V. Orr] discusses methods to reduce anxiety for new

computer users.


Sphinx (search engine) - Performance and scalability

1 * Indexing speed of up to 10-15 MB/sec per core and HDD.



1 * Searching speed of over 500 queries/sec against 1,000,000

document/1.2 GB collection using a 2-core desktop system with 2 GB of

RAM.



1 * The biggest known installation using Sphinx, Boardreader.com, indexes 16 billion

documents.



1 * The busiest known installation, Craigslist, is rumored to serve over

250,000,000 queries/day. or 50 billion page views/month


For More Information, Visit:

• https://store.theartofservice.com/the-scalability-toolkit.html

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