Practical Azure #3: The Case for Windows Azure Drives
In part three of my continuing series, I cover Windows Azure Drives, an abstraction of Windows Azure Blob storage designed to provide a durable layer of storage with the same file I/O semantics of a local drive.
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Comments
Anonymous
November 21, 2012
great intro to CloudDrive ... one thing I wanted to ask, what if I have more than 1 instance ... only 1 instance will be able to mount this drive as writeable at a time. so how do I have a scale out application that many instances all want to write to a drive?Anonymous
November 22, 2012
correct - drives employ a lease model, so can be mounted for write by only one VM/role instance at a time; snapshot can be used for read replicas. The White Paper quoted in the post provides a little insight into some patterns, including having a 'manager' role that oversees the allocation. It may be that each VM instance has its own drive and the 'manager' routes traffic - essentially a sharding pattern. Or, if it's not a heavy-write app, then perhaps all writes go through one instance (w/failover) - this was the original model for the Mongo on Azure implementation. Using SMB - see blogs.msdn.com/.../using-smb-to-share-a-windows-azure-drive-among-multiple-role-instances.aspx - is another option depending on the use case.