Managed Disks
Ultra · Premium SSD v2 · Premium SSD · Standard SSD · Standard HDD
Practice questions for this topic →
Disk types
| Type | Max IOPS | Max throughput | Max size | OS disk? | Use for |
|---|---|---|---|---|---|
| Ultra Disk | 400,000 | 10,000 MB/s | 65,536 GiB | No | SAP HANA, top-tier databases; change performance without restarting the VM |
| Premium SSD v2 | 80,000 | 2,000 MB/s | 65,536 GiB | No | Performance-sensitive production; tune IOPS and throughput independently of size |
| Premium SSD | 20,000 | 900 MB/s | 32,767 GiB | Yes | Production VMs and OS disks |
| Standard SSD | 6,000 | 750 MB/s | 32,767 GiB | Yes | Web servers, light apps, dev/test |
| Standard HDD | 2,000 (3,000 with performance plus) | 500 MB/s | 32,767 GiB | Yes (retiring Sep 8, 2028) | Backup, non-critical |
Facts to know
- Durability and availability (Microsoft Learn): managed disks are designed for 99.999% availability, replicate data three times and provide at least 11 nines of durability; LRS disks are documented at 11 nines and ZRS disks at 12 nines. Microsoft recommends ZRS disks to keep data accessible through a zone outage and when sharing disks between VMs.
- Ultra Disks must be data disks, can only be created empty, range from 4 GiB to 64 TiB, and their IOPS and throughput caps grow with size (4,000 IOPS at 4 GiB, 400,000 from 512 GiB). The default quota is 100 TiB per region per subscription.
- Use Premium SSD for the OS disk when the data disk is an Ultra Disk.
- Using Standard HDD as an OS disk retires on Sep 8, 2028.
Exam Tips
Tick each tip once you can answer it without looking.
“SAP HANA / extreme IOPS, adjust performance live” → Ultra Disk.
“High IOPS database data disk, tune performance independently of size, lower cost than Ultra” → Premium SSD v2.
“Need high-performance OS disk” → Premium SSD. Trap: Ultra and Premium SSD v2 can't be OS disks.
“Dev/test VMs, cheapest reasonable performance” → Standard SSD.
“Disk must survive a zone failure while attached” → ZRS managed disk.
“Failover cluster needs a shared disk” → Azure shared disks.
“Standard HDD OS disks” → Retiring Sep 8, 2028, so plan Standard SSD.
“Compare maximum IOPS” → Ultra 400,000; Premium SSD v2 80,000; Premium SSD 20,000; Standard SSD 6,000; Standard HDD 2,000 (3,000 with performance plus). Trap: Only Premium SSD and below can be OS disks.
“Default Ultra Disk capacity per region per subscription” → 100 TiB (request a quota increase for more). Trap: Ultra Disks are data disks and can only be created empty.
“Disk types that reach 64 TiB” → Ultra Disk and Premium SSD v2 (65,536 GiB). Trap: Premium SSD, Standard SSD and Standard HDD top out at 32,767 GiB.
“Ultra Disk size and performance” → 4 GiB to 64 TiB; IOPS cap grows with size, reaching 400,000 from 512 GiB. Trap: Performance can be changed without restarting the VM.
“Durability and availability of managed disks” → Designed for 99.999% availability; data replicated three times; LRS disks at least 11 nines of durability, ZRS disks at least 12 nines. Trap: Durability isn't the same measure as a VM's uptime SLA.
“Keep disk data accessible through a zone outage” → ZRS managed disks; also use ZRS when sharing disks between VMs. Trap: A shared disk on LRS is a single point of failure.