Jul 20 2008

Redundancy and Failover

Among the more useful innovations in computing, actually invented decades ago, are the twin ideas of redundancy and failover. These fancy words name very common sense concepts. When one computer (or part) fails, switch to another. Doing that seamlessly and quickly versus slowly with disruption defines one difference between good hosting and bad.
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Jul 09 2008

Bandwidth and Server Load, What’s That

Two key performance metrics will impact every web site owner sooner or later: bandwidth and server load.

Bandwidth is the amount of network capacity available, and the term actually covers two different aspects. ”Bandwidth” can meanĂ‚ the measure of network capacity for web traffic back and forth at a given time. Or, it sometimes is used to mean the amount that is allowed for some interval, such as one month. Both are important.

As files are transferred, emails sent and received, and web pages accessed, network bandwidth is being used. If you want to send water through a pipe, you have to have a pipe. Those pipes can vary in size and the amount of water going through them at any time can also vary.

Total monthly bandwidth is a cap that hosting companies place on sites in order to share fairly a limited resource. Companies monitor sites in order to keep one site from accidentally or deliberately consuming all the network capacity. Similar considerations apply to instantaneous bandwidth, though companies usually have such large network ”pipes” that it’’s much less common for heavy use by one user to be a problem.

Server load is a more generic concept.

It often refers, in more technical discussions, solely to CPU utilization. The CPU (central processing unit) is the component in a computer that processes instructions from programs, ordering memory to be used a certain way, moving files from one place to the next and more.

Every function you perform consumes some CPU and its role is so central (hence the name) that it has come to be used as a synonym for the computer itself. People point to their case and say ”That is the CPU”. But, the computer actually has memory, disk drive(s) and several other features required in order to do its job.

Server load refers, in more general circumstances, to the amount of use of each of those other components in total.

Disk drives can be busy fetching files which they do in pieces, which are then assembled in memory and presented on the monitor, all controlled by instructions managed by the CPU.

Memory capacity is limited. It’’s often the case that not all programs can use as much as they need at the same time. Special operating system routines control who gets how much, when and for how long, sharing the total ”pool” among competing processes.

So, how ”loaded” the server is at any given time or over time is a matter of how heavily used any one, or all, of these components are.

Why should you care?

Because every web site owner will want to understand why a server becomes slow or unresponsive, and be able to optimize their use of it.

When you share a server with other sites, which is extremely common, the traffic other sites receive creates load on the server that can affect your site. There’’s a limited amount you can do to influence that situation. But if you”re aware of it, you can request the company move you to a less heavily loaded server. Or, if the other site -which you generally have no visibility to- is misbehaving, it’’s possible to get them moved or banned.

But when you have a dedicated server, you have much more control over load issues. You can optimize your own site’’s HTML pages and programs, tune a database and carry out other activities that maximize throughput. Your users will see that as quicker page accesses and a more enjoyable user experience.

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Jun 26 2008

Web hosting, look before you leap

Companies that offer Internet-connected servers that provide space and bandwidth for a domain, for one or more web sites, are called Web Hosts. Large companies have private networks that allow them to host domains on their own equipment and IP address range. But for the majority of those who want an Internet presence, a ”rented” web host is a necessity.

There are a wide variety of hosting plans available. Some are free, others charge up to a $100 or more per month. Some provide nothing but a tiny amount of disk space and minimal network bandwidth. The web site owner is on his or her own for any thing else. Others offer a range of services, including server and email administration, backups, web site design assistance, troubleshooting and many others.

In the world of web hosting, you may often find yourself sharing a server with anywhere from one to a thousand or more other web sites. That allows the web hosting company to keep equipment and staff expenses lower. Many web sites are simple and low-volume enough that the arrangement works fine. When you or one or more of the others grow, it may be helpful to consider a dedicated server.

A dedicated server, as the name suggests, hosts only your domain. You can put one web site on it, or as many as you wish. You control the access. You may also, as an option, take over much of the server administration yourself. That may save you money on support costs, but cost you considerable time. If you don”t have the expertise, you can end up costing yourself much more than you save.

In order to carry out those administrative functions yourself, even if you hire help, it’’s desirable to have some technical knowledge under your belt. Some of that knowledge will be useful, even for day-to-day tasks apart from dealing with emergencies. FTP, email administration, backup methods and other technical areas are among the more common areas you”ll need to be at least somewhat familiar with.

When your web site grows to a certain size and level of complexity, you”ll begin to find it worthwhile to look at implementing a database. But that brings with it a still higher level of ability, both technical and logistical or creative.

Implementing a database can be relatively simple. Designing one that provides what you want, with decent performance and maintenance that doesn”t become a nightmare, will take some careful thought. Not everyone has the temperament for that type of work, especially those who prefer graphical design, content creation or development, and the many other web site tasks that are part of every implementation.

There are other, more low level administrative matters. Managing disk space, maintaining domain names, dealing with registration and changes, and a number of other ”utilitarian” tasks are also not everyone’’s cup of tea. Some understanding of how DNS works, as well as the design of the Internet itself, are helpful. That provides a good context for understanding the role of some of those tasks.

When you begin to seek out a web host to implement a web site, consider all these factors and look in the mirror. What kind of web hosting you should pursue is determined by a combination of who you are and what’’s being offered. Look before you leap.

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