IBM System Storage DS3500 Introduction And Implementation Manual page 89

Draft Document for Review March 28, 2011 12:24 pm
The DS3500 Storage System only communicates through the use of the WWN. The storage
system is not aware of which host bus adapters are in the same server or in servers that have
a certain relationship, such as a cluster. The host groups, the hosts, and their host ports
reflect a logical view of the physical connections of the SAN, as well as the logical connection
between servers, such as clusters.
With the logical setup defined as previously described, mappings are specific assignments of
logical drives to particular host groups or hosts.
The storage partition is the combination of all these components. It ensures correct access to
the various logical drives even if there are several hosts or clusters connected.
The default host group is a placeholder for hosts that are defined but have not been mapped.
The default host group is also normally used only when storage partitioning is not enabled. If
this is the case, then only one type of operating system must be sharing the logical drives.
Every unassigned logical drive is mapped to the undefined mappings group, which means
that no host (or host port, to be precise) can access these logical drives until they are
mapped.
With Storage Manager, it is possible to have up to 64 storage partitions on a DS3500, which
allows the storage subsystem to provide storage capacity to a number of different
heterogeneous hosts, allowing for greater flexibility and scalability. Note that on DS3500
models, the number of partitions also depends on the premium feature licence that has been
purchased.
For the maximum number of logical drives per partitions for a specific host type see Table 3-4.
Table 3-4 Host logical drive restrictions
Operating system
Windows Server 2003
Windows Server 2008
HP-UX
AIX
Linux
Every mapping of a logical drive to a new host or host group creates a new storage partition.
If additional logical drives are required for an existing host or host group, a new storage
partition is not required. For example, a cluster with two nodes with redundant I/O paths gets
configured as one host group with two hosts. Each host then has two host ports for
redundancy, and several logical drives are mapped to this host group. All these components
represent one storage partition. If another single host system is attached to the same storage
system and other logical drives are mapped to that host, another storage partition then has to
be created for it. If a new logical drive is created and mapped to either the cluster or the single
host, it uses an existing storage partition.
Note: There are limitations as to how many logical drives you can map per host. DS3500
series storage servers will support up to 256 logical drives (including the "access" logical
drive) per partition (although there are also restrictions, depending on the host operating
system) and a maximum of two partitions per host. Keep these limitations in mind when
planning the DS3500 Storage System installation.
Chapter 3. IBM System Storage DS3500 Storage System planning tasks
7914DS3KPlanning_090710.fm
Maximum number of logical drives supported
per partition
32
32
32
32
32
65