However, the le format,
while successful in the areas of digital photography [34] and
large scale visualization [29], is inherently serial. In earlier
work [17] we proposed a three-phase I/O approach to write
data in parallel in IDX le format. The rst phase involved
restructuring of simulation data into large blocks (powers
of 2) while preserving the original multidimensional format.
This facilitated optimized HZ ordering followed by ecient
I/O aggregation (second phase) and ending with actual disk-
level I/O writes (third phase). By adopting this three-phase
I/O we were able to mitigate the shortcomings of small disk
accesses as well as unaligned and discontinuous memory ac-
cess. Figure 1 illustrates the three phases of PIDX.