azure - VM disk

Azure managed disks offer two storage redundancy options:

zone-redundant storage (ZRS), and locally-redundant storage(LRS)

ZRS provides higher availability for managed disks than locally-redundant storage (LRS) does. However, the write latency for LRS disks is better than ZRS disks because LRS disks synchronously write data to three copies in a single data center.

Locally-redundant storage (LRS) replicates your data three times within a single data center in the selected region.

Zone-redundant storage (ZRS) synchronously replicates your Azure managed disk across three Azure availability zones in the region you select.

operating system disk and images:

Virtual machines use virtual hard disks (VHDs) to store their operating system (OS) and data. 

The VM needs the storage account to store its virtual hard disks.