Command Competition - Hitachi VSP F1500 User And Reference Manual

issued in the form of WR or WR-RD. When a command is issued in the form
of RD, it is regarded as an inquiry (equivalent to a SCSI inquiry), and a CCI
recognition character string is returned.

Command competition

The CCI commands are asynchronous commands issued via the SCSI
interface. As a result, if several processes issue these commands to a single
LDEV, the storage system cannot take the proper action. To avoid such a
problem, two or more write commands should not be issued to a single LDEV.
The command initiators should not issue two or more write commands to a
single LDEV unless the storage system can receive commands with
independent initiator number * LDEV number simultaneously.
Command flow
This figure shows the flow of read/write command control for a specified
LBA#.
2-8
Figure 2-5 HORCM and command issue process
Figure 2-6 Command flow
CCI software environment
Command Control Interface User and Reference Guide