Clustering Solutions and Zero Downtime Hosting Pit
There are a number of benchmarks, which we may use to evaluate hosting companies. One of these is, reliability.
Like most things in this life, reliability in web hosting is typically a function of how much we are willing to spend for it. In essence, a “cost-effectiveness” equation needs to be determined and solved.
Reliability can be measured in terms of percentage availability. Industry personnel will talk of reliability in terms of system availability with three (99.9%), four (99.99%) or five nines.(99.999%).
Typically, web-hosting availability exceeding three nines was the purvue of extremely large companies with multiple layers of redundancy built into their network and software systems. However technology has now brought high-availability theory and cost-effective reality into alignment.
High availability can be achieved by removing, as far as possible, any “single point/s of failure”, or, where this is not altogether possible, minimizing the time spent in a “failure” situation.
One of the ways in which small businesses and ISP’s can reasonably avoid single point of failures is by employing server farm clustering and load-balancing solutions.
Webopedia defines server farm clustering as follows:
“A server farm is a group of networked servers that are housed in one location. A server farm streamlines internal processes by distributing the workload between the individual components of the farm and expedites computing processes by harnessing the power of multiple servers.
The farms rely on load-balancing software that accomplishes such tasks as tracking demand for processing power from different machines, prioritizing the tasks and scheduling and rescheduling them depending on priority and demand that users put on the network. When one server in the farm fails, another can step in as a backup.”
It is important to note, that typically, web servers, which are load-balanced in such a manner, display one external IP address to the public Internet, while using internal network IP’s to communicate between the clustered servers and load balancer. Now this is indeed fantastic! Not only do you receive web site peak demand scalability with web server clusters, but you also have the built-in “high uptime availability” component which is so important.
However this is only half of the picture. There are very important cautionary notes to keep in mind.
Where web hosting is concerned, availability depends on two things:
1. Hardware reliability (RAID drives, server clustering etc) within the Data Center;
2. High Bandwidth Internet Connectivity to the Data Center / Network Operating Center (NOC).
Now, with all your well thought out server clustering solutions, what would be the result, if, (as had recently occurred in a very high profile web company), a fire in the Network vicinity had caused the entire Data Center to shut down power for hours. Or, a bandwidth provider to the NOC had router problems. All your websites would be showing the dreaded “Page Cannot be Displayed” page.
The ideal solution therefore would be to employ clustering solutions with servers in entirely different Data Centers with different bandwidth providers. Redundant Data Centers eliminate the NOC itself being a single point of failure. This scenario becomes interesting at this point, because the difficulty of addressing the potential problems now increase exponentially.
We now have to deal with DNS caching, the concept of failover, and how static and dynamic web applications respond to failure events.
Failover and Load balancing are frequently used interchangeably, however they are in fact quite different.
· Load Balancing refers to physically sharing servers capacity, so that one server is not overloaded and swamped with requests.
· Failover however, is the process that manually or automatically switches a failed server or bandwidth provider to a standby server or network if the primary system fails or is temporarily shut down for servicing.
As such, failover software is an important function of mission-critical systems that rely on constant accessibility.
One of the inherent difficulties with failover for Web Hosting companies operating on different networks is the limitations imposed by the DNS caching system.
As DNS records are passed from the original DNS servers (i.e., ns1/ns2.your-domain.com), they are cached or stored at several different ISP’s along the way. Which is why it takes a while for a newly registered domain name to resolve to its IP address.
Each DNS record has a TTL (time to live) setting assigned. By manipulating this value, it is possible to alter how long that particular IP address/ DNS record combo is stored. If your site is on 2 different servers with 2 different IP addresses, you could set the `time to live’ with a value of, say, 2 minutes.
The failover software would check server availability by “pinging” the web server every few minutes to determine whether it’s IP address is responding appropriately. (perhaps by looking for a particular text string in a web page).
If a failure is detected, then the software would pull the non-working web server IP address out of the list of IP addresses assigned to the your web site’s domain name. If/when your web server IP comes back online it would be restored to the list.
With a TTL setting of 2 minutes, theoretically, your web site should be down for just 2 minutes, while switching DNS information to the other web server.
The problem with this scenario, is that, while some ISP’s caching might respond to such low figures, other ISP’s may decide to ignore,(to save on bandwidth utilization), any TTL’s below a certain value, say, 60 minutes. So it is entirely possible that some of your visitors would see your websites and for others, your site would be down for 1 hour or more, even though one of your servers was operating perfectly.
Static non interactive web sites are great candidates for server clustering, but the wicket becomes a bit sticky for dynamically generated sites. Most database application software in general, although having some replication capabilities, are not happy with multiple server master/slave relationships and real time updating between servers. The issue can become very problematic if your site requires frequent updates.
Then there is the problem of how to keep your websites synchronized. Unix/Linux servers have a built in synchronizing software tool called rsync. You can also automate the synchronizing process by setting up a cron job to run periodically. DNS caching and synchronizing issues can be so problematic so as to nullify the advantages of server clustering. For example, a cron job to synchronize your servers every few minutes might very well use up your server capacity.
Your customers will also have to contend with their desktop email client software having dual email addresses for each email account on each web server. e.g. info@server1.net, info@server2.net.
It is important to realize that DNS operates by default in a round robin manner, so that, if you have the same web site on 2 separate servers, it is very likely that server 1 will get 50% of all the web traffic.
Now, this is important for a number of reasons, but one of the principal reasons to keep this in mind, is that, you will not be able to effectively keep a “back-up” site (as some providers would have you believe) which will only be used when the primary server goes down. For e.g. a site saying” we’re sorry our main server is down but you may contact us at: www.yourdomain2.com.
On a final note, hardware based load balancing solutions tend to be quite expensive and also introduce a potential single point of failure into the system, the load balancer itself. There is a very prominent Data Center that began offering load balanced hosting solutions, where the load balancer itself failed on several occasions, although the web servers were operating perfectly. The net effect to the public however, was that the sites was unavailable.
may be obtained as a service model or by purchasing the software yourself. Zoneedit is an example of a service model, and Simplefailover is an example of a software based model which may be purchased on a server license basis.
In conclusion, at this point in time, there are several limiting factors to successfully implementing a “true” high availability multiple server web hosting system. Depending on your clientele and the nature of their web sites,this may indeed be a very viable alternative. For others, simply setting up a server with high quality components, redundant RAID hard drives and a good supply of server spare parts may be the best way to ensure high availability.
Godfrey Heron is the Website Manager of the Irieisle Multiple Domain Hosting Services company. Signup for your free trial, and host multi domains and web sites on one account: http://www.irieisle-online.com
Choosing a Quality Webhost
Choosing a web host is like choosing a place to eat, you want quality food with good, honest, personable service.
If you are anything like me, you’d probably like to have a website on the Internet but you just have no idea how to go about it. All this talk of web hosting, bandwidth, disk space, and other jargon can cause one to say, “This is too complicated and technical, I just wanted to have a place to put all of my favorite skateboarding photos, cool information on ramp designs, and the best places to skate!” To get a website on the Web you have to go through a web host. The question is how do you find the web host for you?
If you type ‘web host’ into your search engine like Google you will get thousands of sites. Hit on one of these and like any product on the market you will see all sorts of persuasive propaganda to incite you to use their company; that is if you can decipher any of the technical jargon that only computer-heads can comprehend. Some web hosts offer free business cards with an account; some probably offer free watches…like all consumer industries you the buyer must beware.
I’m a writer so I’ll use the analogy of a writer’s journal. The journal I like must not be too big or small in book size. It also must have a good amount of space allocated to each day, again not a whole page but not just a few lines. Of course I also want it to be cheap but of a good quality that won’t fall apart while I’m using it, and I hope it would last for posterity. I just want the diary, some nice pictures in it are O.K. but unnecessary especially if it adds to the price.
It’s the same with a web host and web site scenario. You want to get the right deal for you, enough space and enough access to the public that you wish to associate with. As a novice who doesn’t understand all the jargon this can pose a problem. Are you an individual, small business, blog, or a big time corporation? What do you need and how do you get it?
As far as I can tell the web hosting business is a lot like the fast food business. The big corporations have strict guidelines, will offer you special deals, and have monthly ‘cheeseburger specials’. But, I’ve always been more interested in the ‘Mom and Pop’ small time diners who have that real caring human approach. You know you are a customer and a person, not just a number on a sales receipt. I believe the hosting companies are the same.
A smaller hosting company will probably treat its users with more honest integrity as well as having more flexibility in dealing with your individual situation. They can often tailor web site packages to accommodate exactly what you are looking for as well as the ability to update them quickly when your needs change.
My advice is to contact a few of the smaller companies. Look for ones with good reputations or just arbitrarily email them and compare results from different places. Which one do you feel most comfortable with? Go for it; ask as many questions as you can, see how the different hosts differ in their answers. Try one; if it doesn’t work out try another, it’s really easy to move around. Don’t be afraid, you’ve got nothing to lose except the fear itself!
By Jesse S. Somer
M6.Net
www.m6.net
Jesse S. Somer is a novice in the computer world hoping to inform others like him that the Internet is nothing to fear.
Leaders in Web Hosting, M6.net is a strong company that has pioneered in the web hosting industry since 1997. The company started with nothing but a few web sites and less clients; and is now hosting over ten thousand web sites across more than one hundred countries around the world. For reliable web hosting M6.net offers the best value, starting from $4 m/o with 500 MB space, 20GB bandwidth, a 30 Day Money Back Guarantee and 24 hour support.
Changing to new host? No more worries
John’s online business is expanding. His customers are increasing day by day. However, he feels very frustrated at the moment as he finds his website is ‘down’ about every 4th day. Whenever he calls up the support team of his web host, he gets the same old answer that his problem will be rectified soon. If the problems do persist it will surely hamper his business. He has been with his present hosting provider for the last year but now he feels he has to find a new web host as soon as possible because his present hosting package is also not able to meet up with his growing demands. This is not a one-off occurrence that has happened only to John, it happens with many people like him. Changing the web host might become a cumbersome task if John and other people like him don’t know the correct procedure of doing it. So, let’s have a look at the following easy and simple steps:
First of all, it’s very important to have a backup of your website and everything related to it, like databases, scripts etc. It will be very helpful in case there is data loss because of any unforseen reason. Save at least 2 copies of everything and store them separately, so that you can work with one and the other one will function as a backup. You can take backup in various ways. One is by using software programs like a FTP program (e.g. Smart FTP http://www.smartftp.com/) for downloading data.
Now, the time is to look for a new web host that meets all your requirements and provides better technical services than your previous host. Since you have already been through the search procedure it won’t take you much time to come across a reliable hosting company.
Once you have taken a new web-hosting plan and you are ready to upload your web pages, databases etc., check that you have received an IP number, FTP or FrontPage login, and password from your new hosting company. Now, upload all your files to the new server; you are just repeating the same procedure that you’ve done in the past when you uploaded your files for the very first time.
Only a few more steps more and you will be completely done. Before transferring your DNS servers over from your previous host to your new one, debug and test the new site from an individual IP number. Check that all the web pages exist, the links point to the right pages and that all your scripts are running. One important point which people always forget is their domain name expiration date. If you plan to move near the expiration date, it could cause you lots of problems. To be on the safe side, make sure that you have at least 3-4 weeks in hand before the domain name expires, or just renew it for another year.
To transfer domain name service to a new host identify registrar using “WHOis” lookup http://domreg-m6.net/domains/WHois.asp, verify registration of your domain name, identify the name server information for the host your are transferring to, and make changes in the DNS information at the registrar. During this DNS transition period new DNS information has to be propagated throughout the world’s DNS servers. This propagation might take 2-4 days as an International root name server will firstly have to check all the various Domain registrars for updates, and then every ISP provider will update their DNS setting to show the new changes. Not only this, even Internet, i.e. Internet routers and caching engines have to update/clear its DNS cache as well. During this propagation period, you keep your old site running so that the visitors whose ISP provider haven’t updated can still visit your website.
It’s advisable that you don’t cancel your old hosting service during the transition period, as you will need to check your mail from both the hosting providers, as some will direct e-mail to your old server whereas other Internet regions will send mail to your new server. After one or two weeks you can annul the account with your old host.
On the very first notion it sounds like a painful task to find a new web host and make all the necessary changes, but with the steps known, people like John will not find this procedure problematic. With so many automation software packages available, it has now become easier to switch over your web site from old host to new host. If both hosting providers have the same operation system platform, the procedure will become even simpler. But remember, the most important task in the whole host-changing scenario is to find a host that meets your requirements so that you don’t have to go through this entire procedure again in the future.
By Priyanka Agarwal
Hosting evangelist
http://www.m6.net/
Leaders in Web Hosting, M6.net is a strong company that has pioneered in the web hosting industry since 1997. The company started with nothing but a few web sites and less clients; and is now hosting over ten thousand web sites across more than one hundred countries around the world. For reliable web hosting M6.net offers the best value, starting from $4 m/o with 500 MB space, 20GB bandwidth, a 30 Day Money Back Guarantee and 24 hour support.
Unlimited Bandwidth in Web Hosting
Bandwidth explained:
Bandwidth is the amount of data transfer that you are allowed to have for a hosting package i.e. Let’s say you have a web page that is 48KB in size, now each time a user opens your site and goes to that page S/he downloads 48 KB of information on to their computer. If a 100 users view that page one time each then there has been a total of 4800 KB of data transferred from the server on which your files are stored for the computer of users.
Size of web Page: 48 KB
Number of users who viewed the web page: 100
Total amount of data transferred: 48KB * 100 = 4800 KB
Bandwidth is the term that is used to denote the amount of data that has been transferred from your web space.
The amount of bandwidth that you require while choosing a host depends on two factors:
> The size of your site.
> The popularity of your site.
If your site is not very huge and you do not have any audio/video downloads and it’s not very popular i.e. not a lot of people visit your site then you do not really require a lot of bandwidth, on a average a web site uses up only 500 MB of bandwidth per month. Or if your site is small but extremely popular then you might have to go for a web hosting package that offers high bandwidth.
On the other hand if your web site is huge, providing audio/video downloads, as well as being very popular then you would certainly require a huge amount of bandwidth. Let’s say you have a video file that is 150 MB in size and in a single day a 100 visitors download the file. This means that 15 GB of bandwidth will have been used. If you multiply that by 30 days for the month it comes to 450 GB.
The unlimited bandwidth controversy
For some time now a lot of hosting companies are supposedly providing “unlimited bandwidth” for their web hosting packages.
It’s absolutely true, you can have unlimited bandwidth. However, you will need an unlimited amount of money by your side! Jokes apart, if you ever come across such a host it would be best to turn around and run back the way you came from.
Just think, if you can get unlimited bandwidth for $25-30 a month then why aren’t big companies like Sun, Microsoft etc. not hosted there? In fact, why isn’t everyone hosted there? For that matter, if unlimited is a standard feature then why don’t all the hosts offer it? Is it because it is expensive and requires better hardware? No, it’s because some hosts are honest and don’t give in to such gimmicks.
Statistically speaking, a T1 Internet connection (huge broadband) equals approximately 500GB per month and costs around $1200 per month. So how can it be possible to get the same or unlimited for $30 a month?
There are a lot of ways you can be duped by these ‘ unlimited’ hosts; here are just a few of them:
The secret of ‘unlimited’ is actually buried in the Terms of Service by the host. Do not be surprised to find that unlimited = 15 GB.
The host may restrict the sort of files that you can host on their server. Generally image galleries and audio/video files attract a lot more downloads thereby resulting in higher bandwidth consumption. So if there are no files of this type, your site won’t really require a lot of bandwidth.
Some newly opened hosts use it as a scam. They take your money and after a few months when their server starts to become slow or reaches its limit, they run… with your money!
Some hosts outline in their Terms of Service that you can have unlimited bandwidth as long as you qualify for it. i.e. Your site must use less then, let’s say 2 GB of bandwidth in order to qualify for the unlimited bandwidth feature. As soon as your site goes over that limit they either start charging you for it or cut off your downloads altogether.
In life it’s a universal truth that you always get what you pay for, and it’s no different for web hosting.
If a host is using a cheap advertising gimmick like ‘unlimited’ bandwidth they maybe lying about a few other things too. Their ‘dedicated’ support team could be a single person (the hoster itself in most cases) sitting in front of a computer and taking your calls.
Do you really want unlimited bandwidth hosting from hosts that have very limited resources at their disposal? Or, do you want to go for a host that has spent thousands of dollars on setting up a good network infrastructure, servers, and a highly qualified and dedicated support team? The choice ultimately is yours and yours alone.
By Ashish Jain
M6.Net Web Helpers
http://www.m6.net
Leaders in Web Hosting, M6.net is a strong company that has pioneered in the web hosting industry since 1997. The company started with nothing but a few web sites and less clients; and is now hosting over ten thousand web sites across more than one hundred countries around the world. For reliable web hosting M6.net offers the best value, starting from $4 m/o with 500 MB space, 20GB bandwidth, a 30 Day Money Back Guarantee and 24 hour support.
Web Hosting: 4 Factors in Choosing a Host
When choosing a web hosting company there are a whole lot of
different factors that should go into your decision making
process. One of the biggest factors should be:
1) Phone support. Email support is nice, but email
occasionally falls in between the virtual cracks. Getting
someone on the phone when your site goes down can take a lot
of mystery out of the entire process. A lot of the bigger
web hosting companies offer toll free support and weekend
hours to boot. Phone support is a great benefit for any web
hosting client.
2)Another factor to use in deciding whether to use a
particular web hosting company is their history. How long
has this company been in business? Web hosting companies
that have been in existence for less than a year might not
be the best choice. A hosting company with a proven track
record and a ton of happy clients is certainly a good sign
and might work well for you.
3)How about the company’s software? This varies widely
between web hosting companies. I am rather fond of Cpanel
merely because I am used to it, understand where the buttons
are and what the features do. It’s much easier to stick with
something you know than switching to a new User Interface.
Some web hosts offer Frontpage features and others don’t.
Another specific area you might want to research are the
statistics programs. What sort of web statistics software is
included with your web hosting account? Is Awstats included?
This is one area you definitely want to heavily research
before signing up.
4)Fees. I’d rather pay a little more to get all the features
than fight it out with a sub par web hosting company who I
can’t reach if my site goes down. I’ve found decent web
hosting for as cheap as $4 per month but generally pay
around $15 per month if I want all the bells and whistles
that I’ll need to host a larger site. A lot of people worry
about hosting fees, but I’ve had the experience that I
generally get what I pay for. Finally, I’d look carefully at
the web hosting company’s refund policy. Most offer a full
refund if you aren’t happy with your service. If you are
paying for a full year of web hosting up front, you might
want to examine the company’s refund policy in detail.
Richard Martin is a contributing writer at http://www.legalclips.com. LegalClips.com has injury lawyer articles and other legal resources.