VM Storage: Managed Disks

Storage is critical for every virtual machine. Azure Managed Disks abstract away the complexity of managing storage accounts for VM disks, providing high durability, scalability, and integration with Azure's availability features.

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What are Managed Disks?

Azure Managed Disks are block-level storage volumes managed by Azure and used with Azure Virtual Machines. Azure handles the creation, management, and replication of the underlying storage account — you simply specify the disk type, size, and performance tier.

Managed vs Unmanaged Disks

Feature	Managed Disks	Unmanaged Disks (Legacy)
Storage account management	Handled by Azure	You manage storage accounts
Scalability	Up to 50,000 disks per subscription per region	Limited by storage account IOPS
Availability Sets	Aligned to fault domains automatically	Must manually distribute across storage accounts
Snapshots & Images	First-class support	Manual VHD copies
RBAC	Per-disk access control	Storage account level only

Managed Disks are the recommended approach for all new deployments. Unmanaged disks are legacy and should be migrated.

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Disk Types

Azure offers four managed disk types, each balancing performance and cost:

Standard HDD

Property	Value
Max IOPS	500 per disk
Max throughput	60 MB/s per disk
Max size	32 TiB
Best for	Backups, non-critical workloads, dev/test, infrequently accessed data

Standard HDDs are the most cost-effective option but offer the lowest performance. Use them where latency is not a concern.

Standard SSD

Property	Value
Max IOPS	6,000 per disk
Max throughput	750 MB/s per disk
Max size	32 TiB
Best for	Web servers, lightly used enterprise applications, dev/test

Standard SSDs offer better reliability and performance than HDDs at a moderate cost increase. They are a good default choice for non-production workloads.

Premium SSD

Property	Value
Max IOPS	20,000 per disk
Max throughput	900 MB/s per disk
Max size	32 TiB
Best for	Production workloads, databases, latency-sensitive applications
SLA	Enables 99.9% single-VM SLA

Premium SSDs deliver consistent low-latency performance. They are the recommended choice for production workloads, especially databases like SQL Server, Oracle, and MongoDB.

Ultra Disk

Property	Value
Max IOPS	160,000 per disk
Max throughput	4,000 MB/s per disk
Max size	64 TiB
Best for	SAP HANA, top-tier databases, transaction-heavy workloads

Ultra Disks offer the highest performance with independently configurable IOPS and throughput. You can adjust performance dynamically without restarting the VM.

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Disk Roles

Each VM can have multiple disks serving different roles: