Storage Configuration

A well designed storage system is an essential part of a dependable eBox. It must be suitable for your present needs but also be capable of adapting to future changes. It must be reliable, but also be easily repaired if it breaks. You might want it to defend the system against damage caused by broken upgrades. You might require it to provide a high degree of system availability in order to protect your users against hardware failures.

Choosing the most suitable method of managing your disk storage space is a fundamental stage of building your eBox. It may differ depending upon the principal purpose of your server. For example, a machine which is used predominately for serving user and group shares, such as a PDC, might have different storage needs to one which is mainly used as an e-mail server.

The following examples make no attempt to cover all the variations available, rather they cover some typical scenarios that might be commonly used. They are provided to assist you in configuring your own eBox to meet your particular requirements.

The Examples

The examples illustrate the architecture of the storage. The creation of each component is covered in the installation guide. #FIXME LINK TO INSTALLATION GUIDE.

Starting with the simplest, each succeeding example builds upon the previous one as additional features are added. Each starts with a block diagram which shows how the structure of the storage is built up of layers, in a similar manner to a child stacking building blocks on top of each other.

The uppermost layer shows individual storage spaces where all files are ultimately located. It is recommended that you do not allocate all the space available in this layer. This allows the free space to be used to hold a snapshot of your system state prior to applying an upgrade. The snapshot is used to quickly return your system to the pre-upgrade condition if the upgrade is unsuccessful. #FIXME LINK TO SAFEUPGRADE

A further reason for having the unallocated space is the ability to grow any or all of the individual storage spaces into the free space while your system is live and the users active. #FIXME LINK TO LIVESTORAGERESIZE

The second diagram in each example shows a different view of the same storage space. Imagine you are viewing the storage space from directly above. It provides additional details of how it will appear once fully configured. The individual logical volumes, together with their file systems illustrate choices that might be used in an example eBox. Your choices may be different to meet the design requirements of your server.

It is usual that the logical volumes root, swap, and var are created with a recommendation that free space is also made available. Other logical volumes are at your discretion.

Example 1

This is the most basic set-up and uses a single hard disk to store both system and data files.

Hard Disk Layer: This is the only disk in the machine.
Partitions Layer: The hard disk is split into two partitions; /boot is located on sda1 and thereby not part of the volume group.
Volume Group: This is a 'container' for the individual storage spaces.
Logical Volumes: A file system is placed on each one and files are then written to them in the normal way.

A system based on this single disk model will work perfectly well in situations where downtime to conduct repairs is acceptable. If the hard disk fails the entire systems fails. A backup kept on an external device is essential when this configuration is used. It is not recommended in situations where a high degree availability is needed or where backups are stored locally on the same disk.