Azure Elastic SAN addresses a storage problem that often appears only after an Azure environment begins to grow. One virtual machine with one Managed Disk is simple. But as more VMs, databases, and applications appear, each workload can end up with separate disks, separate performance limits, and separate capacity decisions. The result can be inefficient: one workload may be paying for storage performance it rarely uses while another workload needs additional capacity that it cannot borrow. Azure Elastic SAN approaches this differently by providing high-performance block storage through a shared pool.
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WHY SEPARATE DISKS CAN BECOME A PROBLEM
Azure Managed Disks work extremely well for many individual virtual machines. The challenge appears when environments contain many workloads with different performance patterns. A SQL database might experience its highest load at month-end. A reporting server could become busy every morning. Backup workloads might consume significant storage bandwidth overnight while other systems remain almost idle. When every workload is sized individually for its own peak, organizations can end up paying for performance that remains unused for much of the time.
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UNDERSTANDING IOPS AND THROUGHPUT
Two important concepts when discussing storage performance are IOPS and throughput. IOPS means input and output operations per second. It describes how many individual storage operations can be performed each second. Databases frequently generate large numbers of small reads and writes, making IOPS particularly important. Throughput describes how much data can move during a period of time, usually measured in megabytes per second. Large backups, file transfers, and analytical workloads may depend heavily on throughput. Different workloads require different combinations of both.
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THE VM CAN ALSO BECOME THE BOTTLENECK
Adding more or faster disks doesn't automatically solve every storage-performance problem. Azure virtual machines themselves have limits for total disk IOPS and throughput depending on their size. That means you can attach powerful disks and still encounter a bottleneck because the VM cannot process additional storage traffic. The storage might theoretically provide more performance while the path through the virtual machine has already reached its limit.
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WHAT IS A STORAGE AREA NETWORK?
Traditional data centers have addressed similar challenges for years using Storage Area Networks, commonly called SANs. Instead of giving every server completely independent storage infrastructure, organizations create centralized storage systems that multiple servers can access. Azure Elastic SAN brings this familiar shared-storage model into Azure without requiring organizations to purchase storage controllers, install physical storage arrays, wire racks, or maintain SAN hardware themselves.
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WHAT IS AZURE ELASTIC SAN?
Azure Elastic SAN is managed block storage in Azure designed around a shared storage pool. Think of it as a central storage room. Inside that storage environment, individual workloads receive their own separate volumes. The workloads remain logically separated, but the underlying storage capacity and performance can be managed as part of a larger shared resource. A virtual machine can access an Elastic SAN volume similarly to a disk, format it, and store application or database data on it.
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WHAT IS BLOCK STORAGE?
Block storage allows applications to read and write small blocks of data directly. This is particularly important for applications such as SQL Server. A database doesn't simply need somewhere to store ordinary files. It performs large numbers of controlled reads and writes against database files, transaction logs, indexes, and other data structures. Elastic SAN provides this disk-like block-storage model through a network connection.
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HOW ISCSI CONNECTS THE STORAGE
Azure Elastic SAN volumes connect to workloads using iSCSI. iSCSI stands for Internet Small Computer Systems Interface. The terminology sounds complicated, but the basic concept is straightforward: iSCSI carries storage commands between the server and the Elastic SAN across a network connection. The VM requests a particular block of data or sends a write operation. That request travels to Elastic SAN, and the storage system responds. From the workload's perspective, the result behaves much like locally attached block storage.
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ELASTIC SAN VS OTHER AZURE STORAGE SERVICES
Elastic SAN doesn't replace every other Azure storage service. Azure Blob Storage is designed for object storage such as images, videos, backups, and other files. Azure Files provides network-accessible shared file systems. Azure Managed Disks remain a straightforward choice when an individual VM needs its own dedicated block-storage disk. Elastic SAN occupies a different position: centralized high-performance block storage for workloads that can benefit from sharing a larger storage pool.
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THE SHARED PERFORMANCE MODEL
One o...