Slashing AWS Bandwidth Costs by 95%: The dm-cache Story

Upsun dramatically reduced its AWS bandwidth costs by leveraging underutilized local SSD storage on its instances. Using Linux's dm-cache, they implemented a read cache for their Ceph-based network storage. By caching frequently accessed data blocks locally, they minimized costly inter-AZ traffic. Employing a write-through policy ensured data integrity, resulting in a 95% reduction in bandwidth costs, a 30x IOPS improvement, and significant performance gains for their e-commerce applications. The key was exploiting the locality of reference inherent in application I/O patterns.