IBM eServer zSeries 990 Technical Guide

Chapter 2. System structure and design 71

Table 2-10 LPAR storage granularity

Remember that logical partitions are currently limited to a maximum size of 128 GB of

storage.

2.2.11 LPAR Dynamic Storage Reconfiguration (DSR)

Dynamic Storage Reconfiguration (DSR) on z990 servers allows an operating system running

in a logical partition to add (non-disruptively) its reserved storage amount to its configuration,

if any unused storage exists. This unused storage can be obtained when another logical

partition releases some storage, or when a concurrent memory upgrade takes place.

With enhanced DSR, the unused storage does not have to be continuous.

When an operating system running in a logical partition assigns a storage increment to its

configuration, PR/SM will check if there are any free storage increments and will dynamically

bring the storage online.

PR/SM will dynamically take offline a storage increment and will make it available to other

partitions when an operating system running in a logical partition releases a storage

increment.

2.2.12 I/O subsystem

All models have one I/O subsystem. The I/O subsystem should be considered as the physical

entity that encompasses all control functions and all connections to all devices.

The z990 I/O subsystem provides great flexibility and high availability and performance,

allowing:

򐂰 High bandwidth

The z990 I/O subsystem can handle up to 96 GBps; this is four times the z900 server’s

bandwidth. Individual channels can have up to 2 GBps data rates.

򐂰 Wide connectivity

A z990 server can be connected to an extensive range of interfaces, using protocols such

as Fibre Channel Protocol (FCP) for Small Computer System Interface (SCSI), Gigabit

Ethernet (GbE), Fast Ethernet (FENET), 1000Base-T Ethernet, and High Speed Token

Ring, along with FICON, ESCON, and coupling link channels.

򐂰 Concurrent channel upgrades

It is possible to concurrently add channels to a z990 server provided there are unused

channel positions in an I/O cage. Additional I/O cages can be previously installed on an

initial configuration via Plan Ahead, to provide greater capacity for concurrent upgrades.

This capability may help eliminate an outage to upgrade the channel configuration. For

more information about concurrent channel upgrades, see “CUoD for I/O” on page 195.

Total installed memory Partition storage granularity (CS and ES)

Installed memory <= 32 GB 64 MB

32 GB < Installed memory <= 64 GB 128 MB

64 GB < Installed memory <= 128 GB 256 MB

128 GB < Installed memory <= 256 GB 512 MB