Virtual I/O Server
VIOS is a dedicated IBM Power partition that shares one set of physical disk, Fibre Channel and Ethernet adapters out to every other partition on the server. For an IBM i shop that means a Linux partition running an AI model can get its storage and its network connection from VIOS instead of buying its own physical cards.
What does VIOS actually do?
Think of your Power server as an office building and each partition as a tenant. Without VIOS, every tenant needs its own loading dock cut into the outside wall. VIOS is one shared loading dock. Deliveries come in once and get carried to whichever tenant ordered them. IBM's Power 11 documentation puts it plainly: VIOS is software located in a logical partition, and it facilitates the sharing of physical I/O resources between client logical partitions within the server. I/O is short for input and output, meaning disk and network traffic.
- It needs its own partition. IBM says a dedicated logical partition is required for the VIOS software solely for its use.
- It shares SCSI devices, Fibre Channel adapters, Ethernet adapters and optical devices.
- IBM i, AIX and Linux partitions can all be clients of it.
- It is part of the PowerVM Editions hardware feature, not a separate purchase on current servers.
What are the four ways it hands out I/O?
The four sharing features IBM lists for VIOS
- 1. Virtual SCSIClient partitions share disk storage and tape or optical devices that are assigned to the VIOS partition. SCSI is the old storage command language Power still speaks.
- 2. Virtual Fibre Channel with NPIVNPIV is N_Port ID Virtualization. IBM says it lets multiple logical partitions access independent physical storage through the same physical Fibre Channel adapter.
- 3. Shared Ethernet AdapterOne physical network card carries traffic for many partitions, so the AI partition does not need its own network card to reach the rest of your network.
- 4. Shared storage poolsA pool of storage that several VIOS partitions can serve from, instead of mapping every disk by hand to every client.
IBM also lists Active Memory Sharing and Live Partition Mobility as capabilities VIOS provides to client partitions.
Why does an AI partition care?
An AI model on Power 11 runs in a Red Hat Enterprise Linux partition, and that partition still needs somewhere to keep the model and a way to reach your data. Physical slots are the thing you run out of first, because the Spyre Accelerator is a PCIe Gen5 x16 card and the storage and network cards want slots too. IBM's own reason for VIOS is exactly this: it allows creating more logical partitions than there are I/O slots or physical devices available. So the inference partition gets virtual disk and virtual network from VIOS, and the physical slots stay free for the work that has to be physical.
VIOS does not virtualize an accelerator. IBM's list of what VIOS shares covers disk, Fibre Channel, Ethernet and optical devices, and an accelerator card is not on that list. IBM's Spyre Accelerator for Power publication treats Spyre devices like other PCI devices on a Power system, added to or removed from one logical partition. Plan on the card belonging to the Linux partition, and on VIOS covering everything else.
Which VIOS level do I need?
VIOS releases and when IBM stops shipping fixes
- December 2022VIOS 3.1.4. End of fix support was 30 April 2026, so it is already past it.
- November 2023VIOS 4.1.0, built on AIX 7.3 TL 2, generally available 10 November. Supported on Power 8, Power 9 and Power 10. End of fix support 30 November 2026.
- December 2024VIOS 4.1.1. End of fix support estimated 31 December 2027.
- December 2025VIOS 4.1.2, generally available 12 December. IBM lists it on Power 11, Power 10 and Power 9. End of fix support estimated 31 December 2028.
The 2027 and 2028 dates are IBM estimates on its PowerVM VIOS lifecycle page, not commitments. That page also notes it does not give the end of service date for a release.
The useful reading for anyone planning AI work on Power 11 this year is that the two older levels are at or near the end of fix support, and 4.1.2 is the one IBM lists against Power 11. VIOS 4.1 also sped up dynamic partition changes, with IBM reporting up to a 50 percent improvement in the time taken to add or remove processors and memory. That matters here because adding an accelerator card to a running partition is the same kind of dynamic change.
Related Terms
PowerVM
IBM's hypervisor for Power servers, built into system firmware. It is what lets a Linux partition running an AI model sit on the same machine as the production IBM i partition, each with its own processors, memory and cards.
AI Inference Partition
A separate supported operating-system partition used to execute an AI model while an IBM i partition may remain the production application and data source.
Dynamic Logical Partitioning
Dynamic logical partitioning, or DLPAR, moves processors, memory and card slots in and out of a running IBM Power partition without restarting it. IBM documents it for the Spyre Accelerator, so an AI card can join or leave a Linux inference partition while the IBM i production partition keeps working.
Hardware Management Console
The HMC is the console an IBM i shop uses to create the partition an AI model runs in, then hand that partition processors, memory and the PCIe slot holding an accelerator card while production keeps running. IBM Power 11 servers need HMC release V11R1M1110 or later.
AI Workload Placement
The decision about which system, operating environment, and partition executes an AI model or agent, separately from the IBM i application supplying its data.