Veritas InfoScale™ 7.4.1 Virtualization Guide - AIX
- Section I. Overview
- Storage Foundation and High Availability Solutions in AIX PowerVM virtual environments
- Section II. Implementation
- Setting up Storage Foundation and High Availability Solutions in AIX PowerVM virtual environments
- Supported configurations for Virtual I/O servers (VIOS) on AIX
- Installing and configuring Storage Foundation and High Availability (SFHA) Solutions in the logical partition (LPAR)
- Installing and configuring Cluster Server for logical partition and application availability
- Supported configurations for Virtual I/O servers (VIOS) on AIX
- Setting up Storage Foundation and High Availability Solutions in AIX PowerVM virtual environments
- Section III. Use cases for AIX PowerVM virtual environments
- Application to spindle visibility
- Simplified storage management in VIOS
- Configuring Dynamic Multi-Pathing (DMP) on Virtual I/O server
- Configuring Dynamic Multi-Pathing (DMP) pseudo devices as virtual SCSI devices
- Extended attributes in VIO client for a virtual SCSI disk
- Virtual machine (logical partition) availability
- Simplified management and high availability for IBM Workload Partitions
- Implementing Storage Foundation support for WPARs
- How Cluster Server (VCS) works with Workload Patitions (WPARs)
- Configuring VCS in WPARs
- High availability and live migration
- Limitations and unsupported LPAR features
- Multi-tier business service support
- Server consolidation
- About IBM Virtual Ethernet
- Using Storage Foundation in the logical partition (LPAR) with virtual SCSI devices
- How DMP handles I/O for vSCSI devices
- Physical to virtual migration (P2V)
- Section IV. Reference
How DMP handles I/O for vSCSI devices
On the VIO client, DMP uses the Active/Standby array mode for the vSCSI devices. Each path to the vSCSI device is through a VIO server. One VIO server is Active and the other VIO servers are Standby. An Active/Standby array permits I/O through a single Active path, and keeps the other paths on standby. During failover, I/O is scheduled on one of the standby paths. After failback, I/Os are scheduled back onto the original Active path.
The following command shows the vSCSI enclosure:
# vxdmpadm listenclosure all ENCLR_NAME ENCLR_TYPE ENCLR_SNO STATUS ARRAY_TYPE LUN_COUNT FIRMWARE ======================================================================= ibm_vscsi0 IBM_VSCSI VSCSI CONNECTED VSCSI 9 -
The following command shows the I/O policy for the vSCSI enclosure:
# vxdmpadm getattr enclosure ibm_vscsi0 iopolicy ENCLR_NAME DEFAULT CURRENT ============================================ ibm_vscsi0 Single-Active Single-Active
For vSCSI devices, DMP balances the load between the VIO servers, instead of balancing the I/O on paths. By default, the iopolicy attribute of the vSCSI array is set to lunbalance. When lunbalance is set, the vSCSI LUNs are distributed so that the I/O load is shared across the VIO servers. For example, if you have 10 LUNs and 2 VIO servers, 5 of them are configured so that VIO Server 1 is Active and VIO Server 2 is Standby. The other 5 are configured so that the VIO Server 2 is Active and VIO Server 1 is Standby. To turn off load sharing across VIO servers, set the iopolicy attribute to nolunbalance.
DMP dynamically balances the I/O load across LUNs. When you add or remove disks or paths in the VIO client, the load is rebalanced. Temporary failures like enabling or disabling paths or controllers do not cause the I/O load across LUNs to be rebalanced.