COMMA: Coordinating the Migration of Multi-tier Applications

1. COMMA: Coordinating the Migration of Multi-tier Applications JieZheng, T. S. Eugene Ng, Zhaolei Liu Rice University KunwadeeSripanidkulchai NECTEC, Thailand VEE’14

2. Motivation • Live migration can migrate single VM efficiently. • Existing solutions on migrating VMs in a multi-tier application can cause serious performance degradation.

3. Multi-tier Application

4. Split-components Problem

5. Existing Solutions

6. Problem Formulation • Given a set of n VMs in a multi-tier application. • Minimize the performance degradation, or impact. • TM[i,j]: communication traffic rates between VMs prior to the start of migration.

7. COMMA • “COordinating the Migration of Multi-tier Applications” • The first migration coordination system for multiple VMs. • Centralized architecture. • A two-stage scheduling.

8. Two-stage Scheduling • First stage: migrates static content. • Second stage : migrate dynamically generated content.

9. First Stage • Migrate VMs in parallel and finish all VMs’ data migration at the same time. • The amount of migrated data is fixed. • Adjusts each VM’s migration speed according to its virtual disk size

10. Second Stage • Migrate dynamically generated content. • After the first stage, a set of dirty blocks are recorded. • The minimum migration speed of a VM must be greater than its block dirty rate. • VMs are divided into groups.

11. Inter-group Scheduling • To minimize the impact. • Brute-force • O(2n*n!)

12. Inter-group Scheduling(Cont.) • To minimize the impact. • Heuristic • Repeatedly take the largest rate element (rate, VMi, VMj) from the list L, check if VMiand VMjare already in the group set S. • Merge group or insert new groups. • Find the permutation of groups in S with minimal impact • O(n!)

13. Intra-group Scheduling • Starting the VMs’ migration at the same time is not an efficient use of available migration bandwidth.

14. Intra-group Scheduling(Cont.) • Estimate the migration time of each VM. • Assume the minimal required speed for each VM is equal to the VM’s maximal dirty rate • “Finish migration at the same time” • Set different start time to each VM. • Extra available bandwidth will be allocated to the VMs to minimize the total migration time of the group.

15. Evaluation-Setting • Six physical machines. • Kernel-based Virtual Machine(KVM) • Multi-tier application: RUBiS • Includes web server, application server, database server. • Performance metric: average response time of the request from clients per second.

16. Evaluation-Performance • Migrate 3VMs with different strategies.

17. Evaluation-Impact • Migrate 4 VMs from at most three physical machines to the other three.

18. Evaluation-EC2 • Migrate 2 SPECweb2005 VMs from a university campus network to EC2 instances.

19. Conclusion • Propose COMMA, the first coordinated live VM migration system for multi-tier applications. • Based on a two-stage scheduling algorithm to coordinate the migration of VMs. • The goal is to minimize the migration’s impact on inter-component communications.