Zone Redundant Storage (ZRS) for Azure Disk Storage is officially available for Azure Premium SSDs and Standard SSDs in the Canada Central region. ZRS enables synchronous data replication across three availability zones within a region, offering enhanced disk failure tolerance. This feature ensures applications remain operational despite zonal disruptions, obviating the need for application-level data replication across zones. ZRS can be utilized with shared disks, enhancing the availability of clustered or distributed applications such as SQL FCI, SAP ASCS/SCS, or GFS2.
Azure managed disks present two storage redundancy options: ZRS and locally redundant storage (LRS). ZRS offers higher availability compared to LRS by replicating data across multiple zones. In contrast, LRS provides better write latency as it synchronously writes data within a single data center, though it is limited to that center’s physical location.
LRS ensures data is replicated thrice within one data center in a chosen region, guarding against local hardware failures with a durability of 99.999999999% over a year. To safeguard LRS disks from zonal failures, such as natural disasters, it’s recommended to use applications capable of synchronous writes across zones, take frequent backups using ZRS snapshots, and enable cross-zone disaster recovery through Azure Site Recovery, though it does not guarantee zero Recovery Point Objective (RPO).
On the other hand, ZRS offers a durability of 99.9999999999% over a year by replicating data across three separate physical locations within a region, each with its own utilities. This setup allows for recovery from zone failures, maintaining workload operations even if one zone goes down. Shared ZRS disks support enhanced availability for applications by allowing disks to be attached to VMs in different zones.
However, there are limitations. ZRS is only compatible with Premium SSD and Standard SSD managed disks, excluding Premium SSD v2 managed disks. The availability of ZRS disks varies by region, with a list of supported regions provided, indicating its expansion into global markets.
This advancement in Azure Disk Storage underscores a significant step toward improving data resilience and application reliability across diverse geographical locations, catering to a wide range of business continuity and disaster recovery requirements.