IBM System Storage DS3000, Programming Manual

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v
The maximum size of disk pool is 256 TB with controllers having 1 GB or 2 GB cache per controllers
and iSCSI host Interface ports installed.
v
The maximum size of the logical drive in a disk pool is 64 TB.
v
Disk pool cannot be imported from, or exported to another storage subsystem.
Logical Drives
A logical drive is a logical component (object) that is the basic structure that is created on the storage
subsystem to store data. A logical drive is a contiguous subsection of an subsystem that is configured to
meet application needs for data availability and I/O performance. The IBM Storage Manager client
software administers a logical drive as if the logical drive is one “disk drive” for data storage. Logical
drives are identified by names or labels that users choose. The logical drive names can be any
combination of alphanumeric characters, hyphens (-), and underscores (_). The maximum length of a
logical drive name is 30 characters.
The script commands support the following types of logical drives:
v
Standard logical drive – A logical structure that is the principal type of logical drive for data storage.
A standard logical drive is the most common type of logical drive in a storage subsystem.
v
Access logical drive – A factory-configured logical drive in a storage area network (SAN) environment
that is used for communication between the IBM Storage Manager client software and the storage
subsystem controller. The access logical drive uses a logical unit number (LUN) address and consumes
20 MB of storage space. The 20 MB of access logical drive storage space is not available for data
storage.
v Thin logical drive
– A thin logical drive lets you create large virtual logical drive with small physical
storage allocations that can grow over time to meet increased capacity demands. As storage demands
increase, you can increase the amount of physical storage capacity as it is needed. You can create a thin
logical drive in a disk pool only.
Note: You must use the access logical drive only for in-band-managed storage subsystems.
v
FlashCopy logical drive – A logical point-in-time image of another logical drive. A FlashCopy logical
drive is the logical equivalent of a complete physical copy; however, it is not an actual, physical copy.
Instead, the firmware tracks only the data blocks that are overwritten and copies those blocks to a
FlashCopy repository logical drive.
v
FlashCopy repository logical drive – A special logical drive in the storage subsystem that is created as
a resource for a FlashCopy logical drive. A FlashCopy repository logical drive contains FlashCopy data
and copy-on-write data for a particular FlashCopy logical drive.
v Base logical drive
– A standard logical drive from which you create a FlashCopy logical drive. The
term “base logical drive” is used only to show the relationship between a standard logical drive from
which you are taking the point-in-time image and a FlashCopy logical drive.
v
Primary logical drive – A standard logical drive in a Enhanced Remote Mirroring relationship. The
primary logical drive accepts host data transfers and stores application data. When you first create the
mirror relationship, data from the primary logical drive is copied in its entirety to the associated
secondary logical drive.
v
Secondary logical drive – A standard logical drive in a Enhanced Remote Mirroring relationship that
maintains a mirror (or copy) of the data from its associated primary logical drive. The secondary
logical drive remains unavailable to host applications while mirroring is underway. In the event of a
disaster or a catastrophic failure of the primary site, a system administrator can promote the secondary
logical drive to a primary role.
v Mirror repository logical drive
– A special logical drive in a Enhanced Remote Mirroring
configuration that is created as a resource for each controller in both the local storage subsystem and
the remote storage subsystem. The controller stores mirroring information on this logical drive,
including information about remote writes that are not yet complete. A controller can use this
information to recover from controller resets and accidental power shutdown of the storage
subsystems.
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IBM System Storage DS3000, DS4000, and DS5000: Command Line Interface and Script Commands Programming Guide