A Security Prioritized Computational Grid Scheduling Model - Cloud, Grid and High Performance Computing: Emerging Applications - page 96

providing required or higher than the required
security level.
As mentioned in section 2, MinMin is one
of the most popular scheduling algorithms and
is used in real world distributed resource man-
agement systems such as SmartNet (Freund et
al., 1998). The original MinMin is not security
aware and attempts have been made by Song et
al. (2005) to make it secure. MinMin (secured)
works as follows:

• Create a list of the tasks with highest secu-

rity requirement (T high ) from the complete
set of tasks (T Complete ).

• For each task of T high , find the list of the

nodes (N qualified ) which satisfies the security
demand of the task.

• Compute the completion time for each task

of T high on its entire node list (N qualified ).

• For each task, tag the node(s) from the

N qualified that offers minimum completion
time.

• Compute the completion time of all the

tasks on all the nodes.

• Among all such task-node pair, allocate the

task which has the minimum completion
time to the respective node. • Grid node that offers the minimum com-

pletion time while meeting the security de-
mand is tagged for each grid task.

• Remove the task from the T high and T Complete

list.

• Among all such task- node pair, the task

which has the minimum completion time
is allocated to the respective node.

• Modify the begin time (BT) of the resource.

• Repeat the entire process till T high list is

empty. After all the tasks from T high are al-
located new T high is generated and the en-
tire process begins for the new T high . MinMin was not designed to incorporate secu-

rity as a scheduling parameter. The only guiding
parameters for MinMin are size of the task and
speed of the processor. Introducing security made
it behave inefficiently especially under certain
situations. Shorter tasks are scheduled on faster
nodes at priority according to MinMin. In a typi-
cal situation where highly secured machines are
the fastest and there are many shorter tasks with
lower security requirements the performance of
MinMin degrades significantly. The reason is, in
the beginning shorter tasks even with low security
requirement are unnecessarily assigned to the fast-
est node (highly secured) and at the end longer task
also run on overloaded highly secured machines,
as they cannot run on any other machines.
To overcome this shortcoming, we have
modified the Min-Min algorithm to consider
the security requirement as a guiding factor for
the scheduling decisions. The modified Security
Prioritized MinMin (SPMinMin) allocates highest
security demanding tasks first on faster resources.
Its working is as follows:

The Algorithm

The algorithm for the SPMinMin is given in Box 1.

EXPERIMENTAL EVALUATION

To validate and evaluate the performance, simu-
lation experiments have been carried out. The
experimental study considers the complete het-
erogeneous environment e.g. Security requirement
of the tasks; security offered by the nodes, speed
of the nodes and size of the task. Altogether, fol-
lowing possibility for the experimentation exists:

1. High speed nodes are more secured and
heavy tasks require more security.
2. High speed nodes are more secured and
heavy tasks require less security.
3. High speed nodes are more secured no depen-
dency between length of task and security.