Effective Quorum Construction for Consistency Management in Mobile
Effective Quorum Construction for Consistency Management in Mobile Ad Hoc Networks Takahiro HARA Osaka University, Japan
Data Replication in MANETs ► Preventing deterioration of data availability at the point of network partitioning. Data replication. Re p. Consistency management among Re p.
Definition: Consistency �Consistency of data operations on replicas: All read operations can read the latest version of data items (replicas).
Our previous work [IEEE TMC] - Consistency management (1/2) �In a MANET, disappearance of nodes and network partitioning frequently occur. ◦ Read-one, Write-all (Completely synchronized): ◦ Data availability for write operations is very low! Read Write
Our previous work [IEEE TMC] - Consistency management (2/2) �Quorum system ◦ Qi : a set of nodes ◦ Every read operation can access at least a latest replica by performing write/read operations to QW (QR). = Consistency can be maintained. Ex: # of nodes=8, |QW|=5, |QR|=4 Write Rea d
Our previous work [IEEE TMC] - Consistency management (2/2) �Quorum system ◦ Qi : a set of nodes ◦ Every read operation can access at least a latest replica by performing write/read operations to QW (QR). = Consistency can be maintained. Ex: # of nodes=8, |QW|=5, Write/read operations can be performed |QR|=4 even if some MHs are disconnected. Read Data availability can be improved ! [Karumanchi 99, Luo 03, Hara 05] Write
Goal of our work �We address efficient quorum construction and investigate its impact on the system performance. ◦ Investigating the impact of the number of replicas and selection of replica holders (owners) on data availability and traffic.
Effective dynamic quorum construction [Hara’ 10] �System (changeable) parameters: ◦ kj : The number of MHs having the right to replicate Dj (replica owners) �Dynamic quorums based on the rule |QWj| + |QRj| > kj ◦ hj : The max. number of MHs in the write quorum to which the write operation is actually performed (kj ≥ hj). �Other nodes in the write quorum store the information on the time stamp and the hj nodes (index of the latest replica holder). How to select k and h MHs? j j Access frequency based approach (kj: static, hj: dynamic)
Performance study (summary) [Hara’ 10] �Message traffic basically depends on kj (larger kj , higher message traffic). �hj affects the data traffic for both Write/Read. ◦ Write: ◦ Read: �Too larger hj , higher data traffic. larger hj , lower data traffic. small kj shows lower success ratios. kj : Num. of MHs chosen as replica owners hj : Num. of replica owners to which a write is actually performed.
Future directions �Dynamic change of replica owners according to the network topology ◦ Checking periodically the number of replica owners in the majority group and changing replica owners. �Protocol: Quorum-based ? �Quorum patterns construction considering mobility ◦ Node mobility patterns affect the characteristics of network partitioning, e. g. , the number of partitions, partition sizes, and their distribution and stability. ◦ We plan to provide some guideline for effectively constructing quorums.
- Slides: 10