HP XP P9500 Storage - Manual (Page 14)

LDEVs. Then, you can establish virtual THP volumes (THP V-VOLs) and connect them to the individual
THP pools. In this way, capacity to support data can be randomly assigned on demand within the
pool.
THP V-VOLs are of a user-specified logical size without any corresponding physical space. Actual
physical space (in 38-MB pool page units) is automatically assigned to a THP V-VOL from the
connected THP pool as that volume’s logical space is written to over time. A new volume does not
have any pool pages assigned to it. The pages are loaned out from its connected pool to that THP
volume until the volume is reformatted or deleted. At that point, all of that volume’s assigned pages
are returned to the pool’s free page list. This handling of logical and physical capacity is called
thin provisioning. In many cases, logical capacity will exceed physical capacity.
Thin Provisioning Z enhances volume performance by default. This is an automatic result of how
THP V-VOLs map capacity from individual THP pools. A pool is created using from one to 1024
LDEVs (pool volumes) of physical space. Each pool volume is sectioned into 38-MB pages. Each
page is consecutively laid down on a number of RAID stripes from one pool volume. The pool’s
38-MB pool pages are assigned on demand to any of the THP V-VOLs that are connected to that
pool. Other pages assigned over time to that THP V-VOL randomly originate from the next free
page of some other pool volume in the pool.
Setting up a Thin Provisioning Z environment requires a few extra steps. You still configure various
array groups to a desired RAID level and create one or more 3390-V volumes (LDEVs) on each of
them (see
“Creating an LDEV” (page 41) ). Then set up a Thin Provisioning Z environment by creating
one or more THP pools of physical storage space that are each a collection of some of these
3390-V LDEVs (THP pool volumes). This pool structure supports creation of 3390-A Thin Provisioning
Z virtual volumes (THP V-VOLs), where 38-MB pages of data are randomly assigned on demand.
For detailed information, see “Configuring thin provisioning ” (page 54) .
When to use Thin Provisioning Z
Thin Provisioning Z is a best fit in a mainframe environment in the following scenarios:
•
Where the aggregation of storage pool capacity usage across many volumes provides the
best opportunity for performance optimization.
•
For stable environments and large consistently growing files or volumes.
•
Where device addressing constraints are a concern.
Thin Provisioning Z advantages
With Thin Provisioning Z Without Thin Provisioning Z Advantages
You can logically allocate more capacity than
is physically installed. You can purchase less You must purchase physical disk capacity for
expected future use. The unused capacity adds Reduces initial costs
capacity, reducing initial costs and you can add
capacity later by expanding the pool. costs for both the storage system and software
products.
When physical capacity becomes insufficient,
you can add pool capacity without service
interruption. Additional capacity is added without service
interruption. Additional capacity requires
additional addresses and may require
modification of the IOGEN. Reduces
management costs
You can allocate volumes of up to 262,668 cyl
(223,257 GB) regardless of the physical disk
capacity. This improves management flexibility. As the expected physical disk capacity is
purchased, the unused capacity of the storage
system also needs to be managed on the Reduces
management labor
and increases
P9500 product licenses are based on used
capacity rather than the total defined capacity.
storage system and on licensed P9500
products. availability of
storage volumes for
replication
Effectively combines I/O patterns of many
applications and evenly spreads the I/O activity Because physical disk capacity is initially
purchased and installed to meet expected Increases the
performance
across available physical resources, preventing future needs, portions of the capacity may be
14 Introduction to provisioning