Maximum number of virtual hosts in a single web server

I just heard that an US web hosting has over 5000 web sites residing in a single web server. I do not know if the web server has the processing power and memory to serve a large number of concurrent connections. On the other hand, if the web hosting clients know that they are in fact sharing a single web server with over 5000 clients, they can easily figure out what kinds of sevice levels they will have.

So the question is what is the maximum number of virtual hosts that can be supported in a web server. The answer is difficult to guesstimate. I guess it would be below 1000.

These days, a P4 machine with 512 MB and 160GB HD does not cost much for setting up a high performance web server. Why are web hosting companies so mean as not to set up more server. Is it related to the lack of IP addresses ? I guess not. Even if one single IP address in use, it is feasible to make virtual servers behind NAT to boost performance and number of web sites served.


Say "Aloha" to your friends

I find that many young children like to say "Aloha" instead of "hi" or "hello". This probably stems from the popularity of Disney's movie "Stitch".

Aloha is a nice and fancy word. The word "hello" has been used for many centuries. It is good to have a replacement. Next time when you see your friends, try to say "aloha" but not "hi" or "hello".



I have tried using Fedora Core to config servers. Despite Fedora Core can offer rock stable performance, it can not be classified as Enterprise Grade OS. With CentOS, things are changing. Centos is equivalent to Red Hat Enterprise Linux but of course since it is originated from open source, there will not be any technical support. If you are competent with Fedora Core and you would like to try Enterprise Grade Linux OS, Centos is the only choice.


加州 Group X 一位教練

在我認識眾多的加州健身中心教練當中,有一位 Group X 女教練可算是用心良苦。每次 Group X exercise 之後,她總是提醒會員回家後不要吃太多飯、不要飲可樂、奶茶和咖啡,否則我們辛苦運動得來的消耗都會白費。這簡單的幾句說話,正是我們經常忽略的要訣,緊記呀!


Ngong Ping 360 Cable Car

Ngong Ping 360 has opened this month. The biggest attraction of course is riding on the cable car. This is the second cable car facility in town, the first was implemented in Ocean Park about 30 years ago. I plan to ride the cable car by early November. At that time, the weather will be the best around the year and I can enjoy a best view from inside the car.


End of Body Combat 29 launch

Today finished the 2-week launch of Body Combat 29. Altogether I attended over 10 classes in the past 2 weeks.

Overall, BC29 is a great release. Two very special tracks I like most is Wasabi and Vogue. The jump action in track Wasabi is exhaustive and facisinating. For the recovery track no. 6, seems like Les Mills like to pick Madonna's songs. In BC28, it was hung up and in this release, it is Vogue. I guess other Madonna's songs will still be selected for the recovery track in future release.

Since BC 29 is so good, it is difficult for me to expect BC30 to maintain the same quality and standard.

Good work, Les Mills.



I got this nasty virus on my Windows XP probably due to downloading malicious files through p2p networking. This virus disabled command prompt and task manager. Even if you know the name of the malicious files, as they are running in resident memory, without invoking task manager, the background process can not be stopped which renders not being able to delete the files. One way to remove the virus is to boot in safe mode and then delete all the associated files. Another method is to use a boot a Linux live CD, then mount the Windows hard disk and rm the files in Linux environment.


The word "google" added in Oxford Dictionary

The word "google" has been added in dictionary which means searching information from the Internet by means of search engine.

I can think of a few of my examples of using the word google.

1. Google has become so popular that googling is part of my daily online activties second to email.
2. I tried to google about Steve Johnson but can not find any information.
3. Googling is fun.

Enjoy using the word "google" in your daily life.


ipod hang up

In the past week, I experienced crash on my ipod twice. I guessed they were due to the playing of corrupted video files. According to the user manual, whenever there is a hang up on ipod, the remedial action is to press the menu and play button together for 6 seconds and then everything will be reset.


ttcp - Cool Throughtput Test Tool

ttcp is a cool throughput test tool. I am aware that many network administrators use it for network testing and troubling shooting. Even Cisco uses it to test the performance of end-to-end host connection.

For end to end test, the receiving IP has to be put in listen mode. Say, if I want to choose port 1234 for testing with 512 packets only , I would put the machine in receiving mode and speficy the following :

#ttcp -r -n 512 -p 1234 -s

On the transmitting side, the receiving host IP address and port number must be given as follows :

#ttcp -t -n 512 -p 1234 ip_address

It can also generate udp packets by having -u in the comand string. A really handy, cool and useful tool.


33 million network services in a Class C Network

I read a web page about networking and it mentioned that there could be up to 33 million network services in a Class C Network. I was puzzled and started using a calculator to figure it out.

No . of usable IP addresses = 253

No. of TCP Port + UDP port per IP address = 65535

Total number of available network services = 253 x 2 x 65535 = 33.16 million

This is the theoritical situation. In reality, most of the reliable Internet service can not be relied upon UDP. I would therefore better say there could only be 16 .5 million network services in a Class C network.