Memory Operation; Data Protection; Cache Capacity - Hitachi G1500 Hardware Manual

Item Description
1 and 2 Cluster 1

Memory operation

The controller places all read and write data into the cache. The amount of fast-write
data in cache is dynamically managed by the cache control algorithms to provide an
optimum amount of read and write cache, depending on the workload read and write
I/O characteristics.

Data protection

The VSP G1000, VSP G1500, and VSP F1500 storage systems protect the loss of data or
configuration information stored in the cache when electrical power fails. The cache is
kept active for up to 32 minutes by the cache backup batteries while the system
configuration and data are copied to the cache flash memory in the cache backup
modules. For more information, see
backup operations (on page 125)

Cache capacity

The recommended amount of cache to install is determined by the RAID level, the
number of drives installed in the system, and whether Hitachi Dynamic Provisioning
(HDP), Hitachi Dynamic Tiering (HDT), Dynamic Cache Residency (DCR), and Universal
Volume Manager (UVM) are applied. The recommended data cache capacity per Cache
Logical Partition (CLPR) = (CLPR capacity) - (DCR Extent setting capacity per CLPR). When
CLPR is not applied to DP/DT/DCR, install the recommended data cache capacity shown
in the following table.
To configure a system for maximum performance, contact your authorized Hitachi
Vantara representative. See Getting Help in the preface of this manual.
Table 12 Recommended data cache capacity when DP, DT, DCR, and UVM are not
Total logical capacity of external volumes
+ internal volumes per CLPR
Less than 2,900 GB
Less than 2,900 GB
2,900 GB or more
11,500 GB or more
14,400 GB or more
Hitachi Virtual Storage Platform G1000, G1500, and VSP F1500 Hardware Guide
Item
3 and 4
Cache flash memory (on page 58)
.
being used
Chapter 2: Storage system hardware overview
Description
Cluster 0
Recommended data cache capacity per
CLPR
15 GB or more
15 GB or more
16 GB or more
22 GB or more
24 GB or more
Memory operation
and Battery
53