Amazon Web Services' largest region yesterday experienced an eight-hour disruption with the Elastic Block Store (EBS) service that impacted several notable web sites and services.
The lack of fun started at 8:11pm PDT on Sunday, when EBS experienced "degraded performance" in one availability zone (USE1-AZ2) in the US-EAST-1 Region. A subsequent update described the issue as "Stuck IO" and warned that existing EC2 instances may "experience impairment" while new EC2 instances could fail.
US East is the only AWS Region to offer six availability zones – a reflection of its status as the company's first location.
Other AWS services – among them Redshift, OpenSearch, Elasticache, and RDS databases – experienced "connectivity issues" as well.
By 9:17pm, AWS felt that the number of EC2 instances impacted by the issue had plateaued, but users continued to experience difficulties.
By 9:47pm the beginnings of an explanation emerged, as AWS revealed "A subsystem within the larger EBS service that is responsible for coordinating storage hosts is currently degraded due to increased resource contention."