iSCSI disk support for VIOS

The Internet Small Computer Systems Interface (iSCSI) disk is supported in the Virtual I/O Server (VIOS) 3.1.0, or later, and requires FW 860.20, or later. The FW level of 860.20 is supported on POWER8® processor-based systems. For a POWER9™ processor-based systems, the minimum FW level required is FW 910.

The Internet Small Computer Systems Interface (iSCSI) disk provides block-level access to storage devices by carrying SCSI commands over an Internet Protocol network. The iSCSI disk is used to facilitate data transfers over the internet by using TCP, a reliable transport mechanism that uses either IPV6 or IPV4 protocols. The iSCSI disk is used to manage storage over long distances.

The iSCSI support in VIOS allows iSCSI disks to be exported to client logical partitions as virtual disks (vSCSI disks). This support is available in VIOS version 3.1, and later, on both POWER8 and POWER9 systems. If you are using a POWER8 system, the firmware level must be at FW860.20 or later. There are no minimum firmware level requirements for POWER9 systems. POWER9 systems can run on various firmware levels like FW910, FW920, FW930, or later.

VIOS version 3.1 enables Multipath I/O (MPIO) support for the iSCSI initiator. With MPIO support, you can configure and create multiple paths to an iSCSI disk, similar to other protocols. The client logical partition can run either an AIX® or Linux® operating system.

VIOS version 3.1.1 enables support for multiple iSCSI initiators on the VIOS. This support also includes performance enhancements for the iSCSI driver. With multiple iSCSI initiator support, you can create multiple iSCSI software initiator devices on a single AIX operating system instance.

The advantages of configuring multiple iSCSI software initiators are as follows:

  • You can easily create multiple paths for an iSCSI disk that supports Multipath I/O (MPIO). Each path creates its own TCP/IP socket connection. Thereby, the iSCSI traffic is spread across more connections to improve performance through increased concurrent processing.
  • Multiple I/O requests from the iSCSI disk can be logically separated. This reduces the chances of I/O request conflicts between applications.

Limitations

Currently, the iSCSI disk support for VIOS has the following limitations:
  • There is no VIOS boot support using an iSCSI disk.
  • The flat file-based discovery policy is not supported.
  • The iSCSI disk based logical volume (LV) backed devices are not supported.
  • Shared Storage Pools using iSCSI disks as either Repo or Shared Pool disks is not supported.
  • The iSCSI disks or iSCSI based LVs or volume groups (VGs) cannot be used as paging devices for the Active Memory Sharing (AMS) or Remote restart feature.
  • If the backing device is an iSCSI disk, the client_reserve and mirrored attribute are not supported for virtual target devices.
  • On VIOS version 3.1, booting from an iSCSI disk is not supported.

Recommendations

For optimal performance of the iSCSI disk, the following hardware configuration is recommended.
  • A separate private network to access the iSCSI storage.
  • Use of high-speed network adapters and switches (at least 10G is recommended).