Resilire: Achieving High Availability at the Virtual Machine Level

(ABSTRACT) High availability is a critical feature of data centers, cloud, and cluster computing environments. Replication is a classical approach to increase service availability by providing redundancy. However , traditional replication methods are increasingly unattractive for deployment due to several limitations such as application-level non-transparency, non-isolation of applications (causing security vulnerabilities), complex system management, and high cost. Virtualization overcomes these limitations through another layer of abstraction, and provides high availability through live virtual machine (VM) migration: a guest VM image running on a primary host is transparently check-pointed and migrated, usually at a high frequency, to a backup host, without pausing the VM; the VM is resumed from the latest checkpoint on the backup when a failure occurs. A virtual cluster (VC) generalizes the VM concept for distributed applications and systems: a VC is a set of multiple VMs deployed on different physical machines connected by a virtual network. In this dissertation, we first reduce live VM migration downtimes through a memory synchronization technique, called FGBI. FGBI reduces the dirty memory updates which must be migrated during each migration epoch by tracking memory at block granularity. Additionally, it determines memory blocks with identical content and shares them to reduce the increased memory overheads due to block-level tracking granularity, and uses a hybrid compression mechanism among dirty blocks to reduce the migration traffic. We implement FGBI in the Xen VM and compare it with two state-of-the-art VM migration solutions including LLM and Remus, on benchmarks including the Apache webserver and the SPEC benchmark suite. Our experimental results reveal that FGBI reduces the downtime by as much as ≈77% and ≈45% over LLM and Remus respectively, with a performance overhead of ≈13%. We then present a lightweight, globally consistent checkpointing mechanism for VC, which checkpoints the VC for immediate restoration after (one or more) VM failures. VPC predicts the checkpoint-caused page faults during each checkpointing interval, in order to implement a lightweight checkpointing approach for the entire VC. Additionally, it uses a globally consistent checkpoint-ing algorithm, which preserves the global consistency of the VMs' execution and communication states, and only saves the updated memory pages during each checkpointing interval. Our experimental results reveal that VPC reduces the solo VM downtime by as much as ≈45% and reduces the entire VC downtime by as much as ≈50% over competitors including VNsnap, with a memory overhead of ≈9% and performance overhead of ≈16%. The …