VIOS frequently asked questions

VIOS FAQ

VIOS frequently asked questions

1) What is the Virtual I/O Server?

 The Virtual I/O Server is an appliance that provides virtual storage and shared Ethernet adapter capability to client logical partitions on POWER5 systems. It allows a physical adapter with attached disks on the Virtual I/O Server partition to be shared by one or more partitions, enabling clients to consolidate and potentially minimize the number of physical adapters required.

2) Is there a VIOS website?

Yes. The below VIOs website contains links to documentation, hints and tips, VIOS updates and fixes.

     http://www14.software.ibm.com/webapp/set2/sas/f/vios/home.html

3) What documentation is available for the VIOS?

The VIOS documentation can be found online in the below  link.

     http://pic.dhe.ibm.com/infocenter/powersys/v3r1m5/topic/iphb1/iphb1kickoff.htm

4) What is NPIV?

N_Port ID Virtualization(NPIV) is a standardized method for virtualizing a physical fibre channel port. An NPIV-capable fibre channel HBA can have multiple N_Ports, each with a unique identity. NPIV coupled with the Virtual I/O Server (VIOS) adapter sharing capabilities allow a physical fibre channel HBA to be shared across multiple guest operating systems. The PowerVM implementation of NPIV enables POWER logical partitions (LPARs) to have virtual fibre channel HBAs, each with a dedicated world wide port name. Each virtual fibre channel HBA has a unique SAN identity similar to that of a dedicated physical HBA.

The minimum requirement for the 8 Gigabit Dual Port Fibre Channel adapter, feature code 5735, to support NPIV is 110304. You can obtain this image from the http://www-933.ibm.com/support/fixcentral/  

5) What is virtual SCSI (VSCSI)?

Virtual SCSI is based on a client and server relationship. The Virtual I/O Server owns the physical resources and acts as server, or target, device. Physical adapters with attached disks on the Virtual I/O Server partition may be shared by one or more partitions. These partitions contain a virtual SCSI client adapter that sees these virtual devices as standard SCSI compliant devices and LUNs.

6) What is the shared Ethernet adapter (SEA)?

A shared Ethernet adapter is a bridge between a physical Ethernet adapter or link aggregation and one or more virtual Ethernet adapters on the Virtual I/O Server. A shared Ethernet adapter enables logical partitions on the virtual Ethernet to share access to the physical Ethernet and communicate with stand-alone servers and logical partitions on other systems. The shared Ethernet adapter provides this access by connecting the internal VLANs with the VLANs on the external switches.

7) What physical storage can be attached to the VIOS?

See the http://www14.software.ibm.com/webapp/set2/sas/f/vios/documentation/datasheet.html  for supported storage and configurations.

8) What client operating systems support attachment to the VIOS?

1.     AIX 5.3 and AIX 6.1 TL 2

2.     SUSE LINUX Enterprise Server 9 for POWER

3.     Red Hat Enterprise Linux AS for POWER Version 3(update 2 or newer)

4.     Red Hat Enterprise Linux AS for POWER Version 4

5.     IBM i

9) What solutions can be supported using virtual devices and the VIOS?

Virtual SCSI disk devices are standard SCSI compliant devices that support all mandatory SCSI commands. Solutions that have special requirements at the device level should consult the IBM Solutions team to determine if the device meets your requirements.

The VIOS datasheet includes some information on VSCSI solutions.

10) Can SCSI LUNs be moved between the physical and virtual environment as is?

That is, given a physical SCSI device(ie LUN), with user data on it, that resides in a SAN environment; can this device be allocated to a VIOS and then provisioned to a client partition and used by the client as is?

No, this is not supported at this time. The device cannot be used as is, virtual SCSI devices are new devices when created, and the data must be put onto them after creation. This typically would require some type of backup of the data in the physical SAN environment with a restoration of the data onto the virtual disk.

11) In the context of virtual I/O, what do the terms server, hosting, client, and hosted partition mean?

Server and hosting partition is synonymous, as is client and hosted. The server/hosting partition(s) own physical resources and facilitates the sharing of the physical resource amongst the client/hosted partition(s).

12) Do AIX, Linux, and IBM i all provide Virtual I/O Servers?

The Linux and IBM i operating systems do provide various virtual I/O server/hosting features(virtual SCSI, ethernet bridging, etc). AIX does not provide virtual I/O server/hosting capabilities. There is only one product named the Virtual I/O Server. It is a single function appliance that provides I/O resource to client partitions, and does not support general purpose applications.

13) The VIOS appears to have some similarites with AIX, explain.

The VIOS is not AIX. The VIOS is a critical resource and as such, the product was originally based on a version of the AIX operating system to create a foundation based on a very mature and robust operating system. The VIOS provides a generic command line interface for management. Some of the commands in the VIOS CLI may have common names with AIX and Linux commands. These command names were chosen only because they were generic, the flags and parameters will differ. While some of the VIOS commands may drop the user into an AIX-like environment, this environment is only supported for the installing and setup of certain software packages(typically software for managing storage devices, see the VIOS's Terms and Conditions). Any other tasks performed in this environment are not supported. While the VIOS will continue to support it's current user interfaces going foward, the underlying operating system may change at any time.

14) What is the purpose of the oem_setup_env CLI command?

The sole purpose of the oem_setup_env VIOS CLI command is for ease in installing and setting up certain software packages for the VIOS. See the VIOS datasheet for a list of supported VIOS software solutions.

15) What type of performance can I expect from the VSCSI devices?

Please see the section titled "Planning for Virtual SCSI Sizing Considerations" in the VIOS online pubs in InfoCenter.

16) How do I size the VIOS and client partitions?

The VIOS online pubs in InfoCenter include sections on sizing for both Virtual SCSI and SEA. For Virtual SCSI, please see the section titled "Planning for shared Ethernet adapters".

In addition, the WorkLoad Estimator Tool is being upgraded to accommodate virtual I/O and the VIOS.

17) Why can't AIX VSCSI MPIO devices do load balancing?

Typical multipathing solutions provide two key functions: failover and load balancing. MPIO for VSCSI devices does provide failover protection. The benefit of load balancing is less obvious in this environment. Typically, load balancing allows the even distribution of I/O requests across multiple HBA's of finite resource. Load balancing for VSCSI devices would mean distributing the I/O workload between multiple VIOS's. Since the resources allocated to a given VIOS can be increased to handle larger workloads, load balancing seems to have limited benefit.

18) What is APV (Advanced Power Virtualization)?

The Advanced POWER Virtualization feature is a package that enables and manages the virtual I/O environment on POWER5 systems. The main technologies include:

• Virtual I/O Server
  - Virtual SCSI Server
  - Shared Ethernet Adapter
• Micro-Partitioning technology
• Partition Load Manager

The primary benefit of Advanced POWER Virtualization is to increase overall utilization of system resources by allowing only the required amount of processor and I/O resource needed by each partition to be used.

19) What are some of the restrictions and limitations in the VIOS environment?

• Logical volumes used as virtual disks must be less than 1 TB in size.
• Logical volumes on the VIOS used as virtual disks cannot be mirrored, striped, or have bad block relocation enabled.
• Virtual SCSI supports certain Fibre Channel, parallel SCSI, and SCSI RAID devices as backing devices.
• Virtual SCSI does not impose and software limitations on the number of supported adapters. A maximum of 256 virtual slots can be assigned to a single partition. Every virtual slot that is created requires resources in order to be instantiated. Therefore, the resources allocated to the Virtual I/O Server limits the number of virtual adapters that can be configured.
• The SCSI protocol defines mandatory and optional commands. While virtual SCSI supports all of the mandatory commands, some optional commands may not be supported at this time.
• The Virtual I/O Server is a dedicated partition to be used only for VIOS operations. No other applications can be run in the Virtual I/O Server partition.
• Future considerations for VSCSI devices: The VIOS uses several methods to uniquely identify a disk for use in as a virtual SCSI disk, they are:
• Unique device identifier(UDID)
• IEEE volume identifier
• Physical volume identifier(PVID)

Each of these methods may result in different data formats on the disk. The preferred disk identification method for virtual disks is the use of UDIDs.

MPIO uses the UDID method.

Most non-MPIO disk storage multi-pathing software products use the PVID method instead of the UDID method. Because of the different data format associated with the PVID method, customers with non-MPIO environments should be aware that certain future actions performed in the VIOS LPAR may require data migration, that is, some type of backup and restore of the attached disks. These actions may include, but are not limited to the following:

• Conversion from a Non-MPIO environment to MPIO
• Conversion from the PVID to the UDID method of disk identification
• Removal and rediscovery of the Disk Storage ODM entries
• Updating non-MPIO multi-pathing software under certain circumstances
• Possible future enchancements to VIO
• Due in part to the differences in disk format as descibed above, VIO is currently supported for new disk installations only
• Considered when implementing shared Ethernet adapters:
• Only Ethernet adapters can be shared. Other types of network adapters cannot be shared.
• IP forwarding is not supported on the Virtual I/O Server.