COMMA: Coordinating the Migration of Multi-tier Applications Jie Zheng, T. S. Eugene Ng, Zhaolei Liu Rice University Kunwadee Sripanidkulchai NECTEC, Thailand VEE’14

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

Multi-tier Application

Split-components Problem

Existing Solutions

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.

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

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

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

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.

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

Inter-group Scheduling(Cont.) To minimize the impact. Heuristic ◦ Repeatedly take the largest rate element (rate, VM i, VM j ) from the list L, check if VM i and VM j are already in the group set S.  Merge group or insert new groups. ◦ Find the permutation of groups in S with minimal impact ◦ O(n!)

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

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.

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.

Migrate 3VMs with different strategies. Evaluation-Performance

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

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

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.