Planning Gad Pairs And Pair Volumes; Maximum Number Of Gad Pairs - Hitachi G1000 User Manual

system. As a result of specifying External storage > Logical device >
Response time (ms) on the monitoring objects, if the response time
exceeds 100 ms, review the configuration and consider the following actions:
• Lower the I/O load, if the load of I/O of the volumes other than quorum
disk is high in the external storage system.
• Remove factors of the high cache load, if the cache load is high in the
external storage system.
• Lower the I/O load of the entire external storage system, when you do
the maintenance of the external storage system. Alternatively, do the
maintenance of the external storage system with the settings which will
minimize the influences to the I/O in reference to the documents of the
external storage system.
Related topics
• Planning the quorum disk on page 3-10

Planning GAD pairs and pair volumes

This section describes how to calculate the maximum number of GAD pairs,
and the requirements of volumes which is used as a primary volume and a
secondary volume depending on the GAD configuration.
Related topics
• Maximum number of GAD pairs on page 3-16
• S-VOL resource group and storage system: same serial number and
model on page 3-18

Maximum number of GAD pairs

The maximum number of GAD pairs in a storage system is 63,231. This
number is calculated by subtracting the number of quorum disks (at least
one) from the maximum number of virtual volumes (total number of DP-VOLs
plus external volumes: 63,232) that can be defined in a storage system.
If CCI is used in the In-band method, and if one virtual volume is used as a
command device, the maximum number of GAD pairs is 63,230.
Note, however, that the maximum number of pairs in VSP G1000 is subject
to restrictions, such as the number of cylinders used in volumes or the
number of bitmap areas used in volumes.
In the calculation formulas below, "ceiling" is a function that rounds the value
inside the parentheses up to the next integer. "Floor" is a function that
rounds the value inside the parentheses down to the next integer.
Related topics
• Planning GAD pairs and pair volumes on page 3-16
3-16
Hitachi Virtual Storage Platform G1000 Global-Active Device User Guide
Planning for global-active device