A system and method for presenting custom variables to a user of a web analytics system. The probe is mounted in the bracket in such a manner that the probe is guided essentially without contact with a radial spacing through a probe recess a wall of the measuring tube and is positioned in a cross section of a flow-through area of the flow of the measuring tube. The binding site has been found to have particularly good selectivity for glucose. Parity information for each parity drive is co-located or mirrored on the replicated-parity portion of the disk drives for fast access during a read portion of the read-modify-write process.