Managed Linux server profesionals

Xen is really good for running Virtual Private Servers with root access and dedicated RAM. It’s a true virtualization platform that offers multiple local root servers on one physical server hardware. With XEN VPS you get your own virtual server with fully dedicated memory (RAM), process list, file system and a share of central hardware CPU.

Xen Virtual Private Server is perfect for sites that require custom software installation, or even custom daemon configuration that canāt be run on a shared server. Plus, VPS offers better security because you have your own file system that is not shared with other web sites.

However, VPS is a like a small dedicated server - you will probably need skills to manage it. I suggest you read some Linux books and on-line manuals to get familiar with it, otherwise someone may compromise your VPS.

Many folks ask us what is the best platform/OS for web hosting platform? Is it Centos, FreeBSD, Gentoo, Suse or Fedora. While, Centos, FreeBSD, Fedora is more common in USA, SUSE beats deployment statistics in Europe - Germany. Finding Suse and Gento from USA dedicated server companies is somewhat tricky. I am of course not speaking about virtual private servers.

I don’t like much Fedora either because of quick end-of-life (EOF) for updates and upgrading usually costs money, requires downtime and somewhat complex for novice users. So we have rounded down to Centos Linux or FreeBSD. Very good, let’s continue.

FreeBSD is powerful BSD oriented operating system, very reliable, secure (of course if you update it as all other OS) and scalable. Centos is a Redhat Enterprise whitebox clone that is reliable and easy to keep updated due to YUM interface. Much longer EOF comparing to Fedora makes it a much better choice.

While I am more oriented towards Linux - Centos would be my choice of the best OS from the list above, however if you are BSD savvy user - more Unix oriented, go for FreeBSD - it’s powerful, IO-fast, high performance box you could count on.

First, in order to run traceroute on the Windows box you need to launch a command prompt or DOS console.

Type ‘cmd’ and hit enter in Start->Run

To run Traceroute under the Windows you must use traceroute’s command line utility

tracert

traceroute help:

C:\Documents and Settings\Administrator>tracert

Usage: tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout] target_name

Options:
-d Do not resolve addresses to hostnames.
-h maximum_hops Maximum number of hops to search for target.
-j host-list Loose source route along host-list.
-w timeout Wait timeout milliseconds for each reply.

for example to trace the network path to host host.net you should enter

tracert host.net

and hit enter. Voila

If you are installing Mailscanner and Spamassassin from source or some RPMs it’s been know to use Bayesian statistics engine with it’s database kept forever. This fills up /var/spool/MailScanner/spamassassin folder pretty quickly if you have a moderate load SMTP incoming server. To fix this problem and rebuild Bayesian filters you need to change the following value in /etc/MailScanner/MailScanner.conf file

find the following setting:

Rebuild Bayes Every = 0

and replace it with

Rebuild Bayes Every = 12000

This will rebuild Bayesian spamassassin database/files every 200 minutes. You can of course aim for a higher value if you have enough disk space.

We have been playing around with Linux syn cookies to test out the performance and we have came to the following conclusions.

It’s always good to detect SYN floods and then turn on SYN cookies to better use the CPU power - so the SYN flood must be detected and sysctl SYN cookie value set to 1 in the real time. If you have Syn cookies turned on you server CPU and Network stack will be slightly affected, however, no RAM usage will increase in case of SYN flood. The kernel does not allocate the TCP buffers unless there is a positive reply to ACK/SYN packet.
So if you have a dual core box with 1GB RAM and good enough connectivity, you can leave Syn Cookies enabled without much of the performance loss, even if you get quite decent legitimate traffic.

Sysctl Syn cookie protection for Linux can be activated in real time, by:
sysctl -w net.ipv4.tcp_syncookies=1

You can also increase Syn backlog, to let’s say 1536:
sysctl -w net.ipv4.tcp_max_syn_backlog=1536

For FreeBSD you can tune TCP queue length by issuing:
sysctl -w kern.ipc.somaxconn=1024

There are hundreds of blogs that have a lot of daily visitors and require dedicated server custom set-ups to run quickly and without a delay. Many of these blogs quickly outgrow single hardware resources, even if you try to upgrade the server and add more memory, even if you upgrade it to very expensive hardware. It simply doesn’t work and you require more advanced set-up, like front-ends and back-ends that share the load at all levels.

We have seen companies offering one front-end and one back-end MySQL server. Usually, they are run by people who never ran the blogs themselves, thus, no experience and skills required for such set-ups. Load balancing is not that easy, assuming you even know what data synchronization and database replication, or master-slave configuration means. Some “experts” will say round-robin is the key for the load balancing, but we know it is not. You need more complex and more advanced load balancing that works and delivers. You need complex solutions that can easily handle “slashdot” and digg effect - withstand heavy and high load hits when your site is getting hammered by real visitors.

At this time, there are not that many companies offering cluster and true load balancing blog hosting. Multiple front-end boxes and back-end database server data must be kept up to date at any time and quickly responding, otherwise this doesn’t simply make a sense.

There are many guys who ask this question and the answer is not that easy. If you have a real understanding of how Linux or FreeBSD works, you can sure use your skills and apply for unmanaged server. By using unmanaged server you save some bucks and have full control over the server.

But not many know how to properly configure and run server platforms, thus, managed dedicated servers are better choice. However, it will cost you much more - there are some management companies that offer service from $30 and up to $500 per month. Starting from standard OS patching and upgrades, and ending with Apache recompilation and adding modules and tunning the platform for better reliability.