Multipath I/O: a Windows Server feature that reaches the same SAN LUN over more than one physical route, such as several HBAs or iSCSI sessions, to provide failover and spread load, via the Microsoft DSM or one supplied by the storage vendor.
Also called Multipath I/O.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains MPIO in context, with comparison tables and the common traps.
Terms in this definition
- SAN
Block storage carried over its own dedicated network, typically iSCSI or Fibre Channel, which gives ESX hosts LUNs to format as VMFS datastores.
- LUN
Logical unit number, the slot that identifies each data disk attached to a virtual machine. No two disks on the same VM can share one.
- OVER
Gives a T-SQL window function its window: PARTITION BY, ORDER BY and, if wanted, a ROWS or RANGE frame. Rankings and running totals can then be worked out while every row is kept.
- Physical
Describes the concrete, real-world parts that put a logical architecture into effect.
- iSCSI
Protocol that carries block storage over TCP on port 3260. When recovering files, Azure Backup's script mounts recovery point disks as local volumes using it.
- ELT
Extract, load, transform: raw data lands in the target system first and is transformed there. See ETL for the opposite order.
- DSM
Device-specific module: the MPIO plug-in that manages paths to a given storage array. Microsoft's own offers balancing policies including round robin, least queue depth and failover only.
- General-purpose v1
The older storage account kind (
Storage), which lacks access tiers, Archive and premium file shares and retires on 13 October 2026. Converting to ZRS requires first upgrading to GPv2, a one-way change.
Related terms
- LQD
Least Queue Depth sends each I/O down whichever route currently has the shortest backlog. It is one of several MPIO policies, alongside Round Robin, Least Blocks and Fail Over Only.