Calculating the number of cache management devices required for DP-VOLs

A volume that is not a DP-VOL requires one cache management device. The number of cache management devices that a DP-VOL requires depends on the capacity of the V-VOL (capacity of the user area) and the maximum capacity of the cache management device. The maximum capacity of a 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 the cache management device.

Maximum capacity of cache management device

Pool attribute of V-VOL

MB

(TB)

Blocks

Internal volume

3,145,548 MB

(2.99 TB)

6,442,082,304 blocks

External volume

3,145,548 MB

(2.99 TB)

6,442,082,304 blocks

Use the following formula to calculate the number of cache management devices that a DP-VOL requires. In this formula, the user-specified capacity is the user area capacity of a V-VOL.

ceiling(user-specified-capacity / max-capacity-of-cache-management-device)

where

  • ceiling: The value enclosed in ceiling( ) must be rounded up to the nearest whole number.

Note
  • For a DP-VOL with the deduplication or compression function enabled, use twice the number of the cache management devices calculated by this formula.
  • For each deduplication system data volume, 14 cache management devices are used.
Parent Topic
  • Cache management device requirements

    Cache management devices are used to manage the cache associated with volumes (LDEVs). Each volume (LDEV) requires at least one cache management device. An LDEV that is not a DP-VOL requires one cache management device. For an LDEV that is a DP-VOL, you need to calculate the number of cache management devices required.