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Open system host views of the IBM Enterprise Storage Server
ESS supports connection to host systems through an ultra-SCSI adapter of a
fibre-channel adapter. A variety of UNIX-based systems and AS/400 systems
support the ESS as peripheral devices. The following sections discuss how the host
systems view the ESS.
OS/400 operating systems
When attached to an IBM AS/400 with an OS/400 operating system, the ESS can
emulate a 9337. The ESS as an emulated 9337 reports differently to the AS/400
than does a real 9337. The major differences are in the AS/400 Hardware Resource
Manager, some AS/400 service screens, and the AS/400 performance monitors.
LUN reporting is also different:
v A real 9337 reports each of its LUN serial numbers to the AS/400 as a one-digit
v The ESS generates its LUN serial numbers by using a three-digit volume ID plus
Although these differences may be confusing to the user, they do not cause
functional problems with the ESS.
UNIX systems
For UNIX-based systems, the ESS emulates multiple SCSI DDMs. The host system
accesses the virtual drives of the ESS as if they were generic SCSI DDMs. The AIX
operating system contains entries in its object-distribution manager database to
identify the ESS. However, the AIX operating system accesses the ESS through its
generic SCSI DDM. The ESS appears to be a standard physical volume or hdisk to
AIX. The ESS appears similarly to Solaris and HP-UX systems.
When you use ultra- or wide-small computer system interface (SCSI) adapters in
your host systems, a total of 16 SCSI IDs per interface is available on the ESS. The
host system SCSI IDs are known as initiators; the ESS SCSI IDs are the targets.
If you connect only one host system to an ESS SCSI port, the ESS can assign up
to 15 unique target IDs. If you connect the maximum of four host systems to the
ESS, the ESS can only assign up to 12 unique SCSI target IDs.
You can configure an ESS to appear as 64 LUN's per SCSI interface. Define any
LUN size you want from 0 to the maximum array size of 245.5 GB, in 100 MB GB
increments.
When you use fibre-channel adapters to attach to ESS, the ESS can support
connection to a maximum of 128 hosts per fibre-channel port, and a maximum of
physical slot number. It adds the last five digits of the 9337 physical subsystem's
serial number to the total.
The AS/400 uses the last six digits as the controller serial number. This causes a
real 9337 to show on the AS/400 as one controller with up to eight LUNs under
it.
four digits from the ESS physical serial number for the subsystem.
The AS/400 interprets the last two digits of the ESS volume ID as part of the
six-digit controller serial number. This results in the AS/400 generating a unique
controller resource for each ESS LUN.
This resource shows on the AS/400 as multiple controllers with anywhere from
zero to eight LUNs under each controller for each 9337 emulated subsystem.
Most of the extra controllers will have a status of "not connected", and may still
show that "operational" disk units are attached.
Chapter 5. Planning data migration
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