The Challenges of Using Amazon EBS Multi-Attach for Microsoft Failover Clusters

Overview of Amazon EBS and Microsoft Failover Clusters 

Amazon EBS Multi-Attach volumes and Microsoft Failover Clusters are powerful tools in the world of cloud computing and data management. However, integrating these two technologies can be fraught with challenges. This blog post delves into why using Amazon EBS Multi-Attach for Microsoft Failover Clusters is often not the best choice.

The Single AZ Constraint for Robust Failover Clusters

A key limitation of Amazon EBS volumes is their confinement to a single Availability Zone (AZ). For robust failover clusters, deploying instances across multiple AZs is a recommended best practice, something EBS volumes cannot directly support.

High Availability SLA Concerns

While EBS volumes offer a 99.9% availability SLA, this falls short of the 99.99% commonly expected for high availability solutions. AWS does guarantee this higher SLA when deploying instances across multiple AZs, a benefit not extended to single-AZ deployments.

Cost Implications of IO2 Volumes

Windows Failover Clusters with multi-attach EBS volumes necessitate the use of IO2 volumes, which are approximately nine times more expensive than GP3 volumes of similar size and performance. This cost difference is significant, especially for large-scale deployments.

Complexity in AWS Cluster Configuration

Building a cluster in AWS with nodes in the same AZ requires the division of the AZ into multiple subnets to support different virtual IP addresses (VIPs) in the Windows cluster. This complexity, along with the inability to share a single VIP across cluster nodes, adds to the configuration challenges.

SIOS DataKeeper: A Superior Alternative

SIOS DataKeeper emerges as a superior solution, allowing clusters that span subnets while providing the desired 99.99% availability SLA. Not only does it offer more flexible storage options, including the use of GPT3 disks, but it is also far more cost-effective. Clusters using SIOS DataKeeper with GPT3 disks can be around 20% of the cost of similar IO2-based clusters, with enhanced availability.

Superior High Availability with SIOS 

The use of Amazon EBS Multi-Attach volumes in Microsoft Failover Clusters presents several significant challenges, from limited AZ deployment options and lower availability SLAs to higher costs and increased configuration complexity. SIOS DataKeeper offers a compelling alternative, balancing cost, flexibility, and reliability more effectively. For organizations seeking high availability and cost efficiency, exploring options beyond EBS Multi-Attach is a prudent strategy. Contact SIOS for more information.

Reproduced with permission from SIOS