PUBLIC MARKS from lecyborg with tags linux & debian

Our intention is not to build a fail-safe system nor a HA-Linux. We are just using RAID-1 mirrored disks to make sure that the system can be restored easily if 1 disk crashes. The following has been tested only twice (hey, we've got other things to do). It did work for us, it might work for you. It might also make your rats go berserk or just blow your mind.

A RAID device is a Redundant Array of Independent Disks. The concept was developed in 1987 at UC Berkeley and involves the creation of a virtual disk from multiple small disks in order to deliver improved performance and reliability. There are many flavors of RAID and lots of variations in how to implement it. We detail here a specific instance we use: software RAID1 using IDE disks on a Dell PowerEdge box running Debian "sarge" loaded with grub, managed by mdadm, using the ext3 journaling file system.

The system is equipped with 2 similar hard disks (they do not have to be the same but it helps if they are at least similar). The first disk is attached to the primary IDE as master, it will be referenced as /dev/hda. The second disk is attached to the secondary IDE also as master, it will be referenced as /dev/hdc.

This article shows how to run a file-, print-, HTTP proxy- DHCP-, and time server for small and medium enterprises (SME) on one single Debian Sarge system. It is very easy to set up, and management is done with an easy-to-use web interface called eBox so once the system is set up, you can forget about the command line. eBox was developed to administrate advanced services for corporate networks, and it was created for Debian Sarge. I want to say first that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take. I do not issue any guarantee that this will work for you!

There is a great howto about installing Xen on Debian Unstable. It is really easy to do and it runs fine. Nevertheless, on production servers, that's not an optimal solution. Debian Unstable has too many updates and things change too often. On production machines, a Xen host system should be stable, secure and should not need much attention. That is where Sarge comes in. If you pull the Xen packages from backports and install them on Debian stable you've got the best of both worlds. Let's do so!

Lastly on one of the domU's, I had recently upgraded it to Etch. It was rebooted previously and did work. However after going back to Xen with Backports, its network didnt work.

Since several years, I build my own network at home, running 2 to 7 machines at the same time (gateway, firewall, workstation, devstation, servers...). In my flat, it produce a lot of noise, take too many space and consume electricty. I decided to stop that, and to run my all network into a single machine, using virtual machine. The technology that convinced me is Xen.

Creating a Virtual Server - domU There are 3 options of what to run DomU on: 1. File Based Image 2. LVM Based 3. Physical Partition 1. A file based image is the quickest to setup, however has poor/terrible IO performance. The virtual server is limited to the initial size of the image created also. The file based Image can however be easily mounted in a rescue system, and easily backed-up. 2. LVM for domU is the industry standard. After the initial setup of LVM, as described here, it is a dream to manage. LVM partitions can be resized afterwards!!! Due to this "resizing" capability and flexibility, its use for Xen Virtual Servers is ideal. They also have much better IO performance than file-based. I dont know about mounting these partitions however in a rescue system. Something to try out... -). 3. Physical Partitions have the best IO, but are difficult to alter and inflexible.