Scalability targets for premium block blob storage accounts
A premium-performance block blob storage account is optimized for applications that use smaller, kilobyte-range objects. It's ideal for applications that require high transaction rates or consistent low-latency storage. Premium performance block blob storage is designed to scale with your applications. If your scenario requires that you deploy application(s) that require hundreds of thousands of requests per second or petabytes of storage capacity, contact Microsoft by submitting a support request in the Azure portal.
The service-level agreement (SLA) for Azure Storage accounts is available at SLA for Storage Accounts.