Hitachi TAGMASTORE MK-90RD011-25 - Manual (Page 83)

Hitachi Command Control Interface (CCI) User and Reference Guide 65
2.8.7 Command Interface with Hitachi TrueCopy/ShadowImage
When the CCI commands are converted into SCSI commands of a special format, a SCSI
through driver which can send such special SCSI commands to the RAID storage system is
needed. As a result, it is quite possible that support by CCI depends on the OS supplier.
Accordingly, it is necessary to use read/write command that can easily be issued by many
UNIX/PC server platforms. Ioctl() can be used for the following platforms: HP-UX, Linux,
Solaris, Windows, IRIX
® 64, OpenVMS, and zLinux ® .
Format of SCSI commands used. Use the RD/WR command. They should be RD/WR
command valid for special LDEV, since they should be discriminated from the normal RD/WR
command.
Recognition of control command area (LBA#). The host issues control commands through a
special file for raw I/O of a special LDEV. Since the specific LU (command device) receiving
these commands is a normal disk viewed from the SCSI interface, the operating system may
access the control area of its local. The RAID storage system must distinguish such accesses
from the control command accesses. Normally, several megabytes of the OS control area is
used from the initial LAB#. To avoid using this area, a specific LBA# area is decided and
control commands are issued within this area. The command LAB# recognized by the storage
system is shown below, provided the maximum OS control area is 16 MB.
32768 <= LBA# <= 32768 * 2 (In units of block; 512 bytes per block)
The host seeks 32768 * 512 bytes and issues a command.
Seeking position
Command
Area LBA
Special file
(raw I/O volume)
Special LDEV space
OS Control
Area
Command
Target LU
Target LU
Figure 2.33 Relation between Special File and Special LDEV
Acceptance of commands. A command is issued in the LBA area of the special LDEV
explained above. The RD/WR command meeting this requirement should be received
especially as the CCI command. A command is 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.