S-CLONE - Data Storage for Social Networks: A Socially Aware Approach - page 33

Chapter 4
S-CLONE

S-CLONE is a solution we propose to the replication problem, Problem 2.2 ,
discussed in Chap. 2 . S-CLONE can run on top of any given data partition and is
applicable to OSNs that want a fixed budget for the disk space and update cost
required for replication. It provides the same degree of data availability for every
user so that everyone has an equal chance to successfully access data under any
failure condition.
As discussed in earlier chapters, although it is ideal, it is unrealistic to minimize
the total read load of all the servers while simultaneously balancing the server loads,
including read load, write load, and storage load. These objectives are conflicting
with each other. S-CLONE is especially aimed at minimizing the read load as the
primary objective and balancing the write load as the secondary objective. Focusing
on only these objectives, Problem 2.2 is re-expressed as follows:

Problem 4.1 (Replication with Minimum Read Load and Balanced Write
Load). Find the best binary matrix X

L

write T read

minimize
X

;G

subject to 1/ x is 1 p is for 1 i N; 1 s M

X

M

2/ x is D K for 1 i N

s D 1

X

N

X

N

3/ w i .p is C x is / w i .p it C x it / for 1 s<t M

i D 1 i D 1