|
 |
The core is deployed in one data centre as a full mesh topology, so does not have any single points of failure. The perimeter is protected by two firewalls, configured as an active / active pair, each of which is connected to two layer two switches on the external side, which are in turn connected to two core switches. Each of the redundant devices (the firewalls, layer 2 and core switches) are connected with a heartbeat and use either VRRP, NSRP or IEEE802.1q to provide fail over. The core switches are connected to fibre from three different carriers. |
On the internal side each firewall is connected to a second tier of redundant layer 2 switches, which are also connected to each server via bonded network interface cards, thereby providing layer 1 redundancy. All the servers in the core (and the satellites) are highly resilient, utilising RAID 1 and 5 (where appropriate) and redundant power supplies, as well as bonded NIC's. Each server that provides a critical function is deployed as a redundant pair and resides in either the DMZ or the trusted zone. The web servers (which reside in the DMZ) provide the interface that gives the end user with access to their preferences, the reporting engine and the quarantine and are deployed as an active / passive pair. Utilising Heart Beat, a program developed by the Linux HA project, the passive server continually monitors the active server and, should failure occur, will instantaneously make the passive server active. The content on the web servers doesn't change dynamically, so data replication isn't necessary. The Bastion Host also exists in the DMZ and is used to control remote access to the core site. Within the trusted zone the critical servers are the database and storage servers, which utilise dual power supplies, RAID arrays and bonded NIC's, as well being deployed in redundant pairs. The database servers' primary function is to store the data used for reporting and user preferences. They are deployed as an active / passive pair, again utilising Heart Beat to provide the fail over function. Data resides on internal RAID 5 arrays (the operating system on a RAID 1 array) and MySQL provides the replication function. The storage servers' store quarantined and archived email. Deployed in an active/passive pair Heart Beat provides the fail over function, whilst data is stored on a highly resilient Adaptec SANbloc that replicates data across two separate RAID 5 arrays. The other servers in the trusted zone are a monitoring server, a back-up server and an administrative web server, each of which is highly resilient, but not deployed as a redundant pairs. |
 |
|
|
© Checkbridge 2009 |