HP-UX iSCSI Software Initiator Support Guide, HP-UX 11i v1 and 11i v2, July 2005

Chapter 7

The iSCSI Software Interface Driver

iSCSI Software Interface Driver Daemons

iSCSI Software Interface Driver Daemon (iswd)

The iSCSI SWD daemon, iswd, is a user level process that communicates with the iSCSI SWD component

and the network sockets interface. The iSCSI SWD daemon will receive requests to open or close a connection,

then it will use the existing application network socket interface to perform the connection open/close

operation. Once a connection has been established, the iSCSI SWD daemon will use a system call to inform

the iSCSI SWD that the connection is available (on open), the connection attempt failed (on open), or the

connection was successfully closed. Threads forked from the daemon will perform individual connection

establishment.

When the iSCSI SWD daemon initializes, it will bind a module into the connection path in the kernel.

Requests to and from the TCP stack will pass through the kernel component. The kernel component will be

provided with an entry point into the iSCSI SWD, and, on successful open, the iSCSI SWD will be provided

with an entry point into the kernel module. Once the open is complete, data transfers can be made between

the iSCSI SWD and kernel module without iSCSI SWD daemon involvement, thus eliminating copies

between user and kernel space.