The trend in August was probably helped by moving all the space to the DATADISK space token and attracting more interesting data. LOCALGROUP is also heavily used in Manchester.
In the past 4 days we also have applied the XFS file system tuning suggested by John that solves the load on the data servers experienced since upgrading to SL5. The tweak has increased notably the data throughput and reduced the load on the data servers practically to zero allowing us to increase the number of concurrent jobs. This has allowed a bigger job throughput and has had a clear improvement on the job efficiency isolating as most inefficient the very short ones (<10 mins CPU time) and even then the improvement is also notable as it is possible to see from the plots below.
Before applying the tweak
After applying the tweak
This also means we can keep on using XFS for the data servers which has currently more flexibility as far as partition sizes are concerned.