7065Admin_Configure.fm
Draft Document for Review August 30, 2007 12:59 am
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IBM System Storage DS3000: Introduction and Implementation Guide
in stand-alone or clustered mode. The term storage partitioning is somewhat misleading, as it
actually represents a host or a group of hosts and the logical disks they access.
Without storage partitioning, the logical drives configured on a DS3000 storage server can
only be accessed by a single host system or by a single cluster. In most environments, this is
undesirable, as we want to share the same storage system among multiple servers.
Storage partitioning, on the other hand, allows you to create sets, containing the hosts with
their HBAs and the logical drives. We call these sets
storage partitions
. Now the host
systems can only access their assigned logical drives, just as if these logical drives were
locally attached to them. Storage partitioning adapts the SAN idea of globally accessible
storage to the local-storage-minded operating systems.
Storage partitioning lets you map and mask LUNs (that is why it is also referred to as LUN
masking). This means that once you have assigned a LUN to a host, it is hidden from all other
hosts connected to the same storage server, so that access to that LUN is exclusively
reserved for that host.
It is a good practice to do your storage partitioning prior to connecting multiple hosts.
Operating systems like to write their signatures to any device they can access.
Heterogeneous host support means that the host systems can run different operating
systems. But be aware that all the host systems within a particular storage partition must run
the same operating system, as all host systems within a particular storage partition have
unlimited access to all logical drives in this partition. Therefore, file systems on these logical
drives must be compatible with all host systems. To ensure this, the most secure way is to
define your storage partitions to include only hosts running the same operating system, even
though some operating systems might be able to mount foreign file systems.
A storage partition contains several components:
Hosts Groups
Hosts
Host Ports
Logical Drive Mappings
In 8.1.1, “What is a host?” on page 136 we have already discussed the first three terms.
The storage partition is a combination of all these components. It ensures proper access to
the different logical drives even if there are several hosts or clusters connected. Storage
Partitioning associate a Logical Drive to a Host or Host group, so that every logical drive has
it’s own mapping (Logical drive mappings)
Every unassigned logical drive is mapped to the undefined mappings group. This means no
host (or host port, to be precise) can access these logical drives until they are mapped.
A DS3000 supports up to 16 storage partitions (Table 9-1 on page 209). Each time a logical
drive is mapped to a new host or host group, a new storage partition is created automatically.
If you map more logical drives to the same host or host group, this does not count as a new
storage partition. For example, a cluster with two nodes with redundant I/O paths would be
configured as one host group with two hosts. Each host would have two host ports for
redundancy. Several logical drives would be mapped to this host group. All these components
represent one storage partition. If you attach another unclustered host system to the same
storage system and map a logical drive to that host, you create another storage partition. If
you then define a new logical drive and map it to either the cluster or the single host, you are
still using two storage partitions.
