Here is some great information via MitchP on the number and characteristics of SharePoint including their availability supported models (mirroring, etc.)

http://technet.microsoft.com/en-us/library/cc678868(office.14).aspx

Example of content for the config db:

Configuration

The configuration database contains data about SharePoint databases, Internet Information Services (IIS) Web sites, Web applications, trusted solutions, Web Part packages, site templates, and Web application and farm settings specific to SharePoint 2010 Products, such as default quota settings and blocked file types.

Default database name prefix when installed by using the SharePoint Products Configuration Wizard

SharePoint_Config

Location requirements

None

General size information and growth factors

Small.

However, transaction log files are likely to become large. For more information, see Additional notes, below.

Read/write characteristics

Read-intensive

Recommended scaling method

Must scale up; that is, the database must grow larger, because only one configuration database is supported per farm. (Significant growth is unlikely.)

Associated health rules

None

Supported backup mechanisms

SharePoint Server 2010 backup and recovery, SQL Server, and System Center Data Protection Manager (DPM) 2010. The configuration database is a special case for backup and recovery. For more information, see Additional notes below.

Default recovery model

Full. We recommend that you switch the configuration database to the simple recovery model to restrict growth of the log file.

Supports mirroring within a farm for availability

Yes

Supports asynchronous mirroring or log-shipping to another farm for disaster recovery

No