Server Farm Basics

(Archived content. No warranty is made as to technical accuracy. Content may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist)

Note: 
All Internet Protocol (IP) addresses in this paper are fictitiousand are listed as examples only. The public IP address of theInternet Space network used in this paper is not the IP address ofthe actual deployment described. For the purpose of this paper, theIP address of the Internet Space network will be 200.100.1.0, theIP address of the Front End network will be 172.16.1.0, and the IPaddress of the Back End network will be 10.1.1.0.The storage area network (SAN) is one physical unit, but ispartitioned so that each of the two Microsoft SQL Server clustersuses distinct SAN partitions.For details about the hardware and software used in this serverfarm, see the first white paper in this series, Windows SharePoint Services Hosting Configuration and Experience .

The following terms are used in this paper and may be unfamiliarto some users:

• Edge network A network that connectsan Internet data center and a corporate network.
• NAT (Network Address Translation) Analias IP address that identifies a specific node managed by theBIG-IP controller to the external network.
• Predictive mode A dynamic loadbalancing mode that bases connection distribution on a combinationof two factors: number of connections and response time. Serversthat currently host the fewest connections and also have thefastest response times will be assigned more connections.Predictive mode also ranks server performance over time, and passesconnection to servers that exhibit an improvement rather than adecline.
• SNAT (Secure Network AddressTranslation) A routable alias IP address thatone or more nodes can use as a source IP address when makingconnections to hosts on the external network.

Figure 1: Server Farm Configuration

1. Public DNS servers
2. Internet
3. Router (Cisco Systems)
4. Load balancer (F5 Networks BIG-IP)
5. Load balancer (F5 Networks BIG-IP)
6. Front-end Web server farm (six servers)
7. SMTP and DNS server
8. Terminal services, debugging, and administration server
9. SQL Server server 1
10. SQL Server server 2
11. SQL Server server 3
12. SQL Server server 4
13. SAN unit (Hewlett Packard)
14. Active Directory domain controller 1
15. Active Directory domain controller 2
16. MOM server
17. Backup server (Veritas software)
18. Backup tape device
19. HTML transformation server
20. Imaging and installation server (Altiris deploymentserver)
21. Router (Cisco Systems)
22. Edge network

Data Center Architecture Overview

Data Center Architecture Overview

Data Center Architecture Overview

Data Center Design Models

Multi-Tier Model

Server Cluster Model

HPC Cluster Types and Interconnects

Logical Overview

Physical Overview

Web farms in .NET and IIS part 1: a general introduction

Introduction

In this series I’ll try to give you an overview of web farms in the context of IIS and .NET. The target audience is programmers who want to get started with web farms and the MS technologies built around them. I used IIS 7.5 and .NET4.5 in all demos but you should be fine with IIS7.0 and .NET4.0 as well and things should not be too different in IIS8.0 either.

What is a web farm?

A web farm is when you have two servers that perform the same service. You make an exact copy of an existing web server and put a load balancer in front of them like this:

It is the load balancer that catches all web requests to your domain and distributes them among the available servers based on their current load.

The above structure depicts the web farm configuration type called Local Content. In this scenario each web farm machine keeps the content locally. It is up to you or your system administrator to deploy the web site to each node after all the necessary tests have been passed. If the web site writes to a local file then the contents of that file should be propagated immediately to every node in the web farm.

With Local Content the servers are completely isolated. If something goes wrong with one of them then the system can continue to function with the other servers up and running. This setup is especially well suited for distributing the load evenly across the servers.

Disadvantages include the need for an automated content replication across servers which may become quite complicated if you have many elements to replicate: web content, certificates, COM+ objects, GAC, registry entries etc. Also, as mentioned above, if the web site writes to disk then the contents of that file must be propagated to the other nodes immediately. You can alternatively have a file share but that introduces a single point of failure so make sure it is redundant.

Local Content is probably the most common solution for many high traffic websites on the Internet today. There are other options though:

• Shared network content, which uses a central location to manage the content where all web servers in the farm point to that location
• Shared Storage Area Network (SAN) or Storage Spaces in Windows Server 2012, which allow the storage space to be attached as a local volume so that it can be mounted as a drive or a folder on the system

We’ll concentrate on the Local Content option as it is the easiest to get started with and it suits most web farm scenarios out there. If you’re planning to build the next Google or Facebook then your requirements are way beyond the scope of this post anyway: take a look at the web farming frameworks by Microsoft mentioned at the very end of this post. They are most suitable for large websites, especially Windows Azure Services.

Why use a web farm?

The main advantage is reliability. The load balancer “knows” if one of the web servers is out of service, due to maintenance or a general failure, it doesn’t matter, and makes sure that no web request is routed to that particular server. If you need to patch one of the servers in the farm you can simply temporarily remove it from the farm, perform the update and then bring the server up again:

You can even deploy your web deployment package on each server one after the other and still maintain a continuous service to your customers.

The second main advantage of a web farm is to be able to scale up the web tier. In case you have a single web server and you notice that it cannot handle the amount of web traffic you can copy the server so that the load will be spread out by the load balancer. The servers don’t have to be powerful machines with a lot of CPU and RAM. This is called scaling out.

By contrast scaling out the data tier, i.e. the database server has been a lot more difficult. There are available technologies today that make this possible, such as NoSql databases. However, the traditional solution to increase the responsiveness of the data tier has been to scale up – note ‘up’, not ‘out’ – which means adding more capacity to the machine serving as the data tier: more RAM, more CPU, bigger servers. This approach is more expensive than buying more smaller web machines, so scaling out has an advantage in terms of cost effectiveness:

Load balancers

How do load balancers distribute the web traffic? There are several algorithms:

• Round-robin: each request is assigned to the next server in the list, one server after the other. This is also called the poor man’s load balancer as this is not true load balancing. Web traffic is not distributed according to the actual load of each server.
• Weight-based: each server is given a weight and requests are assigned to the servers according to their weight. Can be an option if your web servers are not of equal quality and you want to direct more traffic to the stronger ones.
• Random: the server to handle the request is randomly selected
• Sticky sessions: the load balancer keeps track of the sessions and ensures that return visits within the session always return to the same server
• Least current request: route traffic to the server that currently has the least amount of requests
• Response time: route traffic to the web server with the shortest response time
• User or URL information: some load balancers offer the ability to distribute traffic based on the URL or the user information. Users from one geographic location region may be sent to the server in that location. Requests can be routed based on the URL, the query string, cookies etc.

Apart from algorithms we can group load balancers according to the technology they use:

• Reverse Proxy: a reverse proxy takes an incoming request and makes another request on behalf of the user. We say that the Reverse Proxy server is a middle-man or a man-in-the-middle in between the web server and the client. The load balancer maintains two separate TCP connections: one with the user and one with the web server. This option requires only minimal changes to your network architecture. The load balancer has full access to the all the traffic on the way through allowing it to check for any attacks and to manipulate the URL or header information. The downside is that as the reverse proxy server maintains the connection with the client you may need to set a long time-out to prepare for long sessions, e.g. in case of a large file download. This opens the possibility for DoS attacks. Also, the web servers will see the load balancer server as the client. Thus any logic that is based on headers like REMOTE_ADDR or REMOTE_HOST will see the IP of the proxy server rather than the original client. There are software solutions out there that rewrite the server variables and fool the web servers into thinking that they had a direct line with the client.
• Transparent Reverse Proxy: similar to Reverse Proxy except that the TCP connection between the load balancer and the web server is set with the client IP as the source IP so the web server will think that the request came directly from the client. In this scenario the web servers must use the load balancer as their default gateway.
• Direct Server Return (DSR): this solution runs under different names such as nPath routing, 1 arm LB, Direct Routing, or SwitchBack. This method forwards the web request by setting the web server’s MAC address. The result is that the web server responds directly back to the client. This method is very fast which is also its main advantage. As the web response doesn’t go through the load balancer, even less capable load balancing solutions can handle a relatively large amount of web requests. However, this solution doesn’t offer some of the great options of other load balancers, such as SSL offloading – more on that later
• NAT load balancing: NAT, which stands for Network Address Translation, works by changing the destination IP address of the packets
• Microsoft Network Load Balancing: NLB manipulates the MAC address of the network adapters. The servers talk among themselves to decide which one of them will respond to the request. The next blog post is dedicated to NLB.

Let’s pick 3 types of load balancers and the features available to them:

• Physical load balancers that sit in front of the web farm, also called Hardware
• ARR: Application Request Routing which is an extension to IIS that can be placed in front of the web tier or directly on the web tier
• NLB: Network Load Balancing which is built into Windows Server and performs some basic load balancing behaviour

No additional failure points:

This point means whether the loadbalancing solution introduces any additional failure points in the overall network.

Physical machines are placed in front of your web farm and they can of course fail. You can put a multiple of these to minimise the possibility of a failure but we still have this possible failure point.

With ARR you can put the load balancer in front of your web farm on a separate machine or a web farm of load balancers or on the same web tier as the web servers. If it’s on a separate tier then it has some additional load balancing features. Putting it on the same tier adds complexity to the configuration but eliminates additional failure points, hence the -X sign in the appropriate cell.

NLB runs on the web server itself so there are no additional failure points.

Health checks

This feature means whether the load balancer can check whether the web server is healthy. This usually means a check where we instruct the load balancer to periodically send a request to the web servers and expect some type of response: either a full HTML page or just a HTTP 200.

NLB is only solution that does not have this feature. NLB will route traffic to any web server and will be oblivious of the answer: can be a HTTP 500 or even no answer at all.

Caching

This feature means the caching of static – or at least relatively static – elements on your web pages, such as CSS or JS, or even entire HTML pages. The effect is that the load balancer does not have to contact the web servers for that type of content which decreases the response times.

NLB does not have this feature. If you put ARR on your web tier then this feature is not available really as it will be your web servers that perform caching.

SSL offload

SSL Offload means that the load balancer will take over the SSL encryption-decryption process from the web servers which also adds to the overall efficiency. SSL is fairly expensive from a CPU perspective so it’s nice to relieve the web machine of that responsibility and hand it over to the probably lot more powerful load balancer.

NLB doesn’t have this feature. Also, if you put ARR on your web tier then this feature is not available really as it will be your web servers that perform SSL encryption and decryption.

A benefit of this feature is that you only have to install the certificate on the load balancer. Otherwise you must make sure to replicate the SSL certificate(s) on every node of the web farm.

If you go down this path then make sure to go through the SSL issuing process on one of the web farm servers – create a Certificate Signing Request (CSR) and send it to a certificate authority (CA). The certificate that the CA generates will only work on the server where the CSR was generated. Install the certificate on the web farm server where you initiated the process and then you can export it to the other servers. The CSR can only be used on one server but an exported certificate can be used on multiple servers.

There’s a new feature in IIS8 called Central Certificate Store which lets you synchronise your certificates across multiple servers.

Geo location

Physical loadbalancers and ARR provide some geolocation features. You can employ many load balancers throughout the world to be close to your customers or have your load balancer point to different geographically distributed data centers. In reality you’re better off looking at cloud based solutions or CDNs such as Akamai, Windows Azure or Amazon.

Low upfront cost

Hardware load balancers are very expensive. ARR and NLB are for free meaning that you don’t have to pay anything extra as they are built-in features of Windows Server and IIS. You probably want to put ARR on a separate machine so that will involve some extra cost but nowhere near what hardware loadbalancers will cost you.

Non-HTTP traffic

Hardware LBs and NLB can handle non-HTTP traffic whereas ARR is a completely HTTP based solution. So if you’re looking into possibilities to distribute other types of traffic such as for SMTP based mail servers then ARR is not an option.

Sticky sessions

This feature means that if a client returns for a second request then the load balancer will redirect that traffic to the same web server. It is also called client affinity. This can be important for web servers that store session state locally so that when the same visitor comes back then we don’t want the state relevant to that user to be unavailable because the request was routed to a different web server.

Hardware LBs and ARR provide a lot of options to introduce sticky sessions including cookie-based solutions. NLB can only perform IP-based sticky sessions, it doesn’t know about cookies and HTTP traffic.

Your target should be to avoid sticky sessions and solve your session management in a different way – more on state management in a future post. If you have sticky sessions then the load balancer is forced to direct traffic to a certain server irrespective of its actual load, thus beating the purpose of load distribution. Also, if the server that received the first request becomes unavailable then the user will lose all session data and may receive an exception or unexpected default values in place of the values saved in the session variables.

Other types of load balancers

Software

With software load balancers you can provide your own hardware while using the vendor-supported software for load balancing. The advantage is that you can provide your own hardware to meet your load balancing needs which can save you a lot of money.

We will in a later post look at Application Request Routing (ARR) which is Microsoft’s own software based reverse proxy load balancer which is a plug-in to IIS.

Another solution is HAProxy but it doesn’t run on Windows.

A commercial solution that runs on Windows is KEMP LoadMaster by KEMP Technologies.

Frameworks

There are frameworks that unite load balancers and other functionality together into a cohesive set of functions. Web Farm Framework and Windows Azure Services are both frameworks provided by Microsoft that provide additional functionality on top of load balancing. We’ll look at WFF in a later post in more depth.

Multiple sources.

19 Shocking Facts And Theories About The Bilderberg Group

The Bilderberg Group meets once every year. The last meeting, at the time of this writing, was held in June 2016 at the Taschenbergpalais hotel that is located in Dresden. Up to 150 of the world’s wealthiest and most powerful political leaders attend the annual event. The attendees include royalty, presidents, prime ministers, chief executives of major international conglomerates, media moguls, and world bankers.

The first Bilderberg meeting was held during 1954. The organization was founded with the intent to create powerful connections between European countries and North Americans. The meeting is a secretive, informal discussion about global trends with open communication between the elite members of the world who have massive influence in world affairs.

No statements of any kind are allowed to be made to the press regarding the proceedings or what is talked about at the meeting. There are no meeting minutes taken and no reports of the discussions or official statement about the discussions is produced or made. Anything learned at the meeting can be freely used by any of the members; however, no one is permitted to talk about it.

More than 400 heavily armed guards are there protect the attendees. The event space is hardened with physical barricades and high levels of security. It is this level of high security combined with the extreme secrecy, which makes the conspiracy theorists go wild with speculation about what they actually do at the Bilderberg meetings.

Only those who are invited are permitted to attend the meeting. Everyone invited sees a major career boost after attending a Bilderberg meeting. Bill Clinton attended while he was the Governor of Arkansas and within a year he was President of the United States. Tony Blair became Prime Minister of the UK, four years after going to his first Bilderberg meeting.

19.

FOUNDED BY AN EX-NAZI AND AN AGENT OF THE VATICAN

The co-founders of the Bilderberg Group were two historical figures with checkered backgrounds. They were Prince Bernhard from the Netherlands and Józef Retinger who was a political advisor, originally from Poland, who worked with the Vatican.

Even though throughout his later adult life, up until his death in 1984, Prince Bernhard claimed he was never a Nazi. A historian, Annejet van der Zijl, found documents at the Humboldt University in Berlin, which prove Prince Bernhard was indeed a Nazi Party member until 1934 when he left school to work for the huge German chemical company named IG Farben. IG Farben did atrocious things in support of the Nazis including making the poisonous gas used to kill people in the German death camps.

Józef Retinger was a secret spy for the Vatican. He was expelled from allied countries for his activities in association with the Jesuits. He later went on to create the Council of Europe during 1949, which became part of the foundational movement, which eventually led to the formation of the European Union.

18.

SERIOUS CONFLICTS OF INTEREST

The Bilderberg Group publishes on its website a simple list of the items that will be discussed at an upcoming meeting, without giving any further details.

For the 2016 meeting here is the list of the topics up for discussion:

China, current events, cybersecurity, Europe (growth, immigrants, reform, unity and vision), geopolitics of energy and commodities, lower classes and the middle class, Middle East, Russia, technological innovation, US political climate, economy, debt, growth, and reform.

The Bilderberg Group also publishes a list of the attendees. By comparing the attendees with the proposed agenda is it easy to see the potential conflicts of interest. A high probability must exist of shady “back-room” deals and influence peddling. Hilary Clinton always attends and she has received millions of dollars in “speaker’s fees” from other attendees.

The Chairman of BP, Carl-Henric Svanberg, and the group chief executive of BP, Robert Dudley, the vice-chairman of Galp Energia from Portugal, and the CEO of Royal Dutch Shell all met with finance ministers and top political leaders. After the Bilderberg Group meeting, they do not report back to their respective governments about what happened.

Other attendees of the 2016 meeting included former European Commission President José Manuel Barroso, former U.S. Secretary of State Henry Kissinger, U.S. Senator Lindsey Graham, Christine Lagarde who is the Director of the International Monetary Fund, German Defense Minister Ursula von der Leyen, German Interior Minister Thomas de Maizière, German Finance Minister Wolfgang Schäuble, King Willem-Alexander of the Netherlands, a former head of the CIA, General David Petraeus, and a former head of MI6, Sir John Sawers.

17.

THE WHO’S WHO OF THE WORLD

*I consider this a "must read, book mark, mull it over and read the full article again" type of deal > http://tinyurl.com/yc6f43cb

The government just admitted it will use smart home devices for spying

f you want evidence that US intelligence agencies aren’t losing surveillance abilities because of the rising use of encryption by tech companies, look no further than the testimony on Tuesday by the director of national intelligence, James Clapper.

As the Guardian reported, Clapper made clear that the internet of things – the many devices like thermostats, cameras and other appliances that are increasingly connected to the internet – are providing ample opportunity for intelligence agencies to spy on targets, and possibly the masses. And it’s a danger that many consumers who buy these products may be wholly unaware of.

“In the future, intelligence services might use the [internet of things] for identification, surveillance, monitoring, location tracking, and targeting for recruitment, or to gain access to networks or user credentials,” Clapper told a Senate panel as part of his annual “assessment of threats” against the US.

Clapper is actually saying something very similar to a major study done at Harvard’s Berkman Center released last week. It concluded that the FBI’s recent claim that they are “going dark” – losing the ability to spy on suspects because of encryption – is largely overblown, mainly because federal agencies have so many more avenues for spying. This echoes comments by many surveillance experts, who have made clear that, rather than “going dark”, we are actually in the “golden age of surveillance”.

Privacy advocates have known about the potential for government to exploit the internet of things for years. Law enforcement agencies have taken notice too, increasingly serving court orders on companies for data they keep that citizens might not even know they are transmitting. Police have already been askingGoogle-owned company Dropcam for footage from cameras inside people’s homes meant to keep an eye on their kids. Fitbit data has already been used in court against defendants multiple times.

But the potential for these privacy violations has only recently started reaching millions of homes: Samsung sparked controversy last year after announcing a television that would listen to everything said in the room it’s in and in the fine print literally warned people not to talk about sensitive information in front of it.

 Follow

Parker Higgins 

✔@xor

Left: Samsung SmartTV privacy policy, warning users not to discuss personal info in front of their TV
Right: 1984

4:35 AM - 8 Feb 2015

 
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While Samsung took a bunch of heat, a wide array of devices now act as all-seeing or all-listening devices, including other television models, Xbox Kinect, Amazon Echo and GM’s OnStar program that tracks car owners’ driving patterns. Even a new Barbie has the ability to spy on you – it listens to Barbie owners to respond but also sends what it hears back to the mothership at Mattel.

Then there are the rampant security issues with the internet of things that allow hackers – whether they are criminal, government or something in between – to access loads of data without any court order, like the creeps who were eavesdropping on baby monitors of new parents. Just a few weeks ago, a security researcher found that Google’s Nest thermostats were leaking users’ zipcodes over the internet. There’s even an entire search engine for the internet of things called Shodan that allows users to easily search for unsecured webcams that are broadcasting from inside people’s houses without their knowledge.

While people voluntarily use all these devices, the chances are close to zero that they fully understand that a lot of their data is being sent back to various companies to be stored on servers that can either be accessed by governments or hackers.

While Clapper’s comments are generating new publicity for this privacy worry, the government has known about the potential to exploit these devices for a long time. The then CIA director David Petraeus made clear that intelligence agencies would use theinternet of things to spy on people back in 2012, saying:

Items of interest will be located, identified, monitored and remotely controlled through technologies such as radio-frequency identification, sensor networks, tiny embedded servers, and energy harvesters – all connected to the next-generation internet using abundant, low-cost, and high-power computing.

As Wired put it, Petraeus was expressing excitement the CIA would soon be able spy on you through your dishwasher.

Author and persistent Silicon Valley critic Evgeny Morozov summed up the entire problem with the internet of things and “smart” technology in a tweet last week:

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Evgeny Morozov @evgenymorozov

In case you are wondering what "smart" - as in "smart city" or "smart home" - means:

Surveillance
Marketed
As
Revolutionary
Technology

7:45 PM - 31 Jan 2016

 
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While internet-connected devices are not going away – it’s a certainty they will only get more prevalent – it’s important that companies make them as secure as the end-to-end encryption the FBI director loves to complain about, and that we press the government to enact strict new rules to prevent our privacy from being invaded thanks to the weakest link among televisions or dolls or thermostats that line billions of homes around the world.

Since you’re here …

… we have a small favour to ask. More people are reading the Guardian than ever but advertising revenues across the media are falling fast. And unlike many news organisations, we haven’t put up a paywall – we want to keep our journalism as open as we can. So you can see why we need to ask for your help. The Guardian’s independent, investigative journalism takes a lot of time, money and hard work to produce. But we do it because we believe our perspective matters – because it might well be your perspective, too.

I appreciate there not being a paywall: it is more democratic for the media to be available for all and not a commodity to be purchased by a few. I’m happy to make a contribution so others with less means still have access to information.Thomasine F-R.

If everyone who reads our reporting, who likes it, helps to support it, our future would be much more secure.

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Topics

• Internet of things
 
• Trevor Timm column

• Surveillance
 
• Data protection
 
• Smart homes
 
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