1) How many servers are on the cluster platform?
At present there are 2 racks of servers, disk arrays, load balancers, switches and secondary rackmount UPSs in the cluster (these connect to the secondary power input on critical servers to supplement the primary datacentre UPS). The actual server count fluctuates continuously as we add servers or take them down for maintenance/upgrades, all of which is seamless to the end user. For instance 2 weeks ago we rebooted every Linux web server in turn in a single evening for kernel upgrades. Customers were not aware of this, nor did they need to be.
2) What specification are the servers?
The majority of web servers are Dell R200 Quad Core Xeons with 8GB RAM. There are also some Dell R710 Dual Quad Core Xeons. Mail and database servers are a mix of Dell 1950s, 2950s and R710s, all with SCSI RAID 5/10.
3) How many users are there?
The system is scalable, so as the demand on the servers increases we add more.
4) Whats the redundancy/backup like?
There are 2 storage nodes which data is synchronised between at regular intervals. Currently these are in an N+1 configuration (one master, one backup) with failover to the backup node but we are working towards splitting the load between the two devices during normal operation to increase performance. At no time will the total usage be allowed to exceed the capacity of single node so that the system can run adequately on a single node if one were to fail.
5) Is that backup offsite?
Data is replicated nightly over a fibre optic connection to another datacentre in case of some kind of disaster at our primary site (fire, flood, explosion) however the risk of this is very slim. The datacentre uses advanced VESDA equipment with VM200 fire suppression which will put out a fire before it really takes hold. The datacentre is not on a flood plain and access restrictions are extremely strict to prevent unauthorised access or sabotate. The datacentre is guarded and monitored by CCTV 24x7x365.
6) Where are the servers?
Our primary datacentre site for the clustered hosting is Bluesquare 2 in Maidenhead where we have a private suite.