Giles R. Frazier

Sharing FCP adapters through virtualization

The IBM System z9TM and its predecessors pioneered server virtualization, including the sharing of data storage subsystems among the virtual servers of a host computer using the channel-sharing capabilities of FICON® channels in Fibre Channel (FC) fabrics. Now industry-standard Small Computer System Interface (SCSI) devices in storage area networks must be shared among host computers using the Fibre Channel Protocol (FCP), and this has been problematic with virtual servers in a host computer. To apply the power of server virtualization to this environment, the IBM System z9 implements a new FC standard called N_Port Identifier Virtualization (NPIV). IBM invented NPIV and offered it as a standard to enable the sharing of host adapters in IBM servers and FC fabrics. With NPIV, a host FC adapter is shared in such a way that each virtual adapter is assigned to a virtual server and is separately identifiable within the fabric. Connectivity and access privileges within the fabric are controlled by identification of each virtual adapter and, hence, the virtual server using each virtual adapter. This paper describes the problem prior to the development of NPIV, the concept of NPIV, and the first implementation of this technique in the FCP channel of the IBM System z9.

SCSI initial program loading for zSeries

This paper describes a new kind of initial program loading (IPL) for IBM zSeries® servers. The new IPL protocol expands the set of input/output devices that can be used during IPL to include Small Computer System Interface (SCSI) Fibre Channel protocol (FCP) disk devices (SCSI disks). We begin by describing several new challenges resulting from the use of SCSI disks during IPL, followed by a brief overview of new concepts we have applied to the IPL process to overcome these challenges. We continue with a step-by-step description of the processes executed during SCSI IPL, the tools used, the disk format, the parameters required, and related topics. Since SCSI IPL is supported for virtual machines instantiated by the z/VM® operating system, some unique features of this capability are described. Finally, we describe a variation of SCSI IPL that enables the contents of memory to be dumped onto a SCSI disk.

Magnetic tape velocity variation measurement using a read while write head

Magnetic tape velocity variations are determined with a read while write head by measuring the frequency difference between the write current signal and the playback signal from the read gap. This frequency difference may correspond to either tape acceleration or velocity, depending on the period at which the tape velocity is varying, and it can be measured by observing beat frequencies on a storage oscilloscope.