SIZE value

[ianb-mp]

Documentation says this about SIZE variable:

the size should be at least 25 times the read/write bandwidth to avoid the caching impacting the result.

It's unclear to me how I would calculate this number. Could you provide an example of how this number would be calculated? My system uses 4x 10k SAS drives in a RAID 10 array. The RAID controller has 2G cache.