IBM System storage DS6000 Series Redbook page 559

For 2105, a Rank is either assigned to server 0 or server 1, depending on the Array Site
location. A 2105 Rank is assigned to one of 32 possible LSS IDs, depending on device
adapter pair location and storage type configuration.
For 1750, an Extent Pool is assigned to server 0 or server 1. A Rank that is configured
from any Array Site can be assigned to a server 0 or 1 Extent Pool. Array Site position and
device adapter pairs are not factors for the Rank-to-Extent Pool assignment. A volume
that is created from a server 0 Extent Pool is assigned to an even-numbered LSS ID. A
volume that is created from a server 1 Extent Pool is assigned to an odd-numbered LSS
ID. A user must define at least two Extent Pools (0 and 1), but can define as many Extent
Pools as there are Ranks. For 2105, a user can delete a Rank, but cannot delete a
volume. For 1750, a user can delete a single volume, Rank, or Extent Pool. The 1750 CLI
showrank and showextpool commands include a metrics parameter that returns the
performance counter values for a specified Rank or Extent Pool ID. The metrics parameter
provides the means to monitor Rank and Extent Pool performance statistics.
Note 2
A 1750 fibre-channel port is configured for either SCSI-FCP or FICON protocol. Like 2105,
a FICON port is restricted to the point-to-point/switched fabric topology setting. A FICON
I/O port is used for System z host attachment, but cannot be configured as a PPRC path.
A FICON port must be configured for anonymous access mode, meaning that any System
z host system port (WWNN/WWPN) has unrestricted access to all CKD volumes, up to
8192 volumes.
Like 2105, a 1750 fibre-channel SCSI-FCP I/O port can be configured for either the
point-to-point/switched fabric or FC-AL connection topologies. A port that uses the
point-to-point/switched fabric topology can be simultaneously used for OS host system I/O
and for PPRC path configurations. The Fibre Channel SCSI-FCP IO port only allows
"identified" host system ports to access volumes. A host system port WWPN must be
identified (registered) to each 1750 IO port through which volume access is intended. Host
system port WWPN identification is accomplished by the mkhostconnect CLI command.
Note 3
A 1750 Storage Unit can contain up to 8192 volumes, where either they are all FB or all
CKD, or there are 4096 CKD volumes and 4096 FB volumes. A 2105 Storage Unit can
contain up to 4096 FB volumes and 4096 CKD volumes. Otherwise, the 2105 and 1750
volume definitions and characteristics are essentially identical.
For 1750 CKD PAV volumes, the CLI list and show commands identify both the original
base and current base volume assignments. The original and current base concept exists
for 2105, but specific relationships are not identified in the output.
The 1750 CLI provides a specific set of volume commands for each storage type, fixed
block or CKD, as a means to clarify input parameter and output device adapter definitions.
The 1750 CLI showfbvol and showckdvol commands include a metrics parameter that
returns the performance counter values for a specified volume ID. The metrics parameter
provides the means to monitor volume performance statistics.
Note 4
The 2105 volume access commands concern volume ID assignment to a SCSI-FCP host
port initiator, or WWPN. For 1750, volume IDs are assigned to a user defined volume
group ID (mkvolgrp and chvolgrp). A volume group ID is then assigned to one or more
host system ports (mkhostconnect and chhostconnect) as a means of completing the
volume access configuration.
The volume group construct also exists in the 2105 internal code, but the construct is not
externalized by the 2105 Specialist or CLI commands.
Appendix D. CLI migration
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