Recommended configurations for IBM iSeries hosts

This section provides recommended configurations for IBM^® iSeries™ hosts. This section only applies to i5/OS partitions.

You can use the following configurations for each feature code:

For feature codes 2766 and 2787 (2 Gb adapters):
- Install feature code 2766, which is an I/O adapter, in the IBM iSeries system unit or in the high-speed link (HSL) PCI I/O towers.
- Install only one 2766 adapter per I/O processor (IOP) because it requires a dedicated IOP. No other I/O adapters are supported under the same IOP.
- Install only two 2766 adapters per multiadapter bridge.
For feature code 5760 (4 Gb adapter):
- Install feature code 5760, which is an I/O adapter, in the IBM iSeries system unit or in the high-speed link (HSL) PCI I/O towers.
- Install only one 5760 adapter per I/O processor (IOP) because it requires a dedicated IOP. No other I/O adapters are supported under the same IOP.
- Install only two 5760 adapters per a multiadapter bridge.
Note: 4 GB adapters can connect to a DS6000, but will auto negotiate and only run at 2 GB per second.

The following is an example of the output of the logical hardware resources of the hardware service manager that are associated with the IOP.

Opt Description                     Type-Model	  Status          Resource Name

Combined Function IOP               2843-001     Operational     CMB04
Storage IOA                         2766-001     Operational     DC18
Disk Unit                           1750-A82     Operational     DD143
Disk Unit                           1750-A81     Operational     DD140
Disk Unit                           1750-A81     Operational     DD101

The following is an example of the output for the hardware service manager auxiliary storage hardware resource detail for the storage unit.

Description........................:  Disk unit
Type-Model.........................:  1750-A82
Status.............................:  Operational
Serial number......................:  75-1409194
Part number........................:  
Resource name......................:  DD143
licensed machine code.............:  FFFFFFFF
Level..............................:  
PCI bus............................:  
  System bus.......................:  35
  System board.....................:   0
  System card......................:  32
Storage............................:  
  I/O adapter......................:   6
  I/O bus..........................:   0
  Controller.......................:   1
  Device...........................:   1

You can define the storage unit LUNs as either protected or unprotected. From a storage unit physical configuration view point, all IBM iSeries volumes are RAID-5 or RAID-10 volumes and are protected within the storage unit. When you create the IBM iSeries LUNs by using the IBM System Storage™ DS Storage Manager or DS CLI, you can create them as logically protected or unprotected.

Table 1 shows the disk capacity for the protected and unprotected models. Logically unprotecting a storage LUN, allows the iSeries host to perform remote load source mirroring to that device. Because the load source is mirrored on an external LUN, the storage unit can copy or transfer this load source as a disaster recovery backup. When you use the iSeries tool kit, an iSeries host in a remote location, using a copy of the original load source, can recover this load source and start running as if this recovery box were the original source host.

Table 1. Capacity and models of disk volumes for IBM iSeries
Size	Type	Protected model	Unprotected model	Release support
8.5 GB	1750	A01	A81	Version 5 Release 2 or later
17.5 GB	1750	A02	A82	Version 5 Release 2 or later
35.1 GB	1750	A05	A85	Version 5 Release 2 or later
70.5 GB	1750	A04	A84	Version 5 Release 2 or later
141.1 GB	1750	A06	A86	Version 5 Release 3 or later
282.2 GB	1750	A07	A87	Version 5 Release 3 or later

Starting with i5/OS Version 5 Release 3, IBM iSeries supports multipath attachment through fibre channels as part of the base i5/OS support. Version 5 Release 3 uses the existing host adapters (feature code 2766 and 2787, and 5760). New paths are automatically detected, configured by the system, and immediately used. If a disk is initially set up as a single path and a second path is added, the resource name of the disk unit is modified from DDxxx to DMPxxx to reflect that it now has more than one path to the disk unit. No changes are required by the user on the iSeries to make use of the new path. Multipath connections can be made direct connect or through a fabric.

Note: Multipath is not supported on an external disk unit acting as a System i load source.

For additional information on fabric zoning recommendations see DS6000™ fabric zoning.

To activate multipath on an iSeries host, use the IBM System Storage DS Storage Manager.

With i5/OS Version 5 Release 3 and later, path information is available for the disk unit hardware configuration from iSeries Navigator.

To improve the availability of fibre-channel disks (when there is more than one 2766, 2787, or 5760 I/O adapter), use the following configuration guidelines to help you achieve good DS6000 iSeries I/O performance:

Spread iSeries LUNs across as many logical ranks as possible on different DS6000 processors:
- Use no more than 500 I/O operations per second per rank.
- Assign I/O critical iSeries applications to DDMs with speeds of 15000 rpm or more.
- Create ranks of eight DDMs, if you are formatting RAID 5 ranks.
Use the Disk Magic Analysis tool to calculate the smallest LUNs size as possible to allow more iSeries-active I/O, without effecting device response times.
Assign no more than 500 GB of storage to each iSeries I/O adapter.
For SAN attachments, do not connect more than four iSeries I/O adapters to a single I/O attachment port.
Use only one fibre-channel IOP/IOA pair per multiadapter bridge. Do not use more than six IOP/IOA pairs per high-speed loop (HSL). Use 64-bit, 133 MHz PCI-X slots.