HP XP P9500 Storage - Manual (Page 24)

Shared memory requirements
If configuring thin provisioning, Thin Provisioning requires dedicated shared memory for the V-VOL
management area.
The V-VOL management area, which is automatically created when shared memory is added, is
an area used to store information for associating pool-VOLs and THP V-VOLs.
If Thin Provisioning is used, at least 16 GB of shared memory consisting of two sections is required.
The memory capacity allocated to each part is as follows:
•
Basic part: 8 GB
•
Thin Provisioning: 8 GB
If Smart Tiers is used, shared memory for Thin Provisioning and Smart Tiers is necessary. At least
24 GB of shared memory consisting of two sections is required. The memory capacity allocated
to each part is as follows:
•
Basic part: 8 GB
•
Thin Provisioning: 8 GB
•
Smart Tiers: 8 GB
If Thin Provisioning and Smart Tiers are used, a pool or V-VOL capacity can be created and the
shared memory can be expanded depending on its status. If you use a pool or V-VOL which has
a capacity greater than 1.1 PB, the shared memory must be installed. Before the shared memory
is uninstalled, all Thin Provisioning and Smart Tiers pools must be deleted.
The required shared memory is installed by your HP representative.
About cache management devices
Cache management devices are associated with volumes (LDEVs) and used to manage caches.
One volume (LDEV) requires at least one cache management device. An entire system can manage
up to 65,280 cache management devices. A THP V-VOL may require more than one cache
management device. This topic describes how to calculate the number of cache management
devices.
Calculating the number of cache management devices required by a THP V-VOL
The number of cache management devices that a THP V-VOL requires depends on the capacity of
the V-VOL (capacity of the user area) and the maximum capacity of cache management device.
The maximum capacity of cache management device depends on the pool attribute (internal volume
or external volume) associated with V-VOL. The following table explains the relationship between
the pool attribute and the maximum capacity of cache management device.
Maximum capacity of cache management device
Maximum capacity
(in blocks)
Maximum capacity
(in MB)
Pool attribute
6,442,426,368 3,145,716 Internal volume
(2.99 TB)
6,442,426,368 3,145,716 External volume with Mixable set to
Enabled
(2.99 TB)
8,589,901,824 4,194,288 External volume with Mixable set to
Disabled
(3.99 TB)
24 Introduction to provisioning