IBM DS8900F, Introduction And Planning Manual

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ESE Extent Threshold
The percentage that is compared to the actual percentage of storage capacity available for ESE
customer extent allocation when determining the extent pool ESE extent status.
ESE Extent Status
One of the three following values:
• 0: the percent of the available thin-provisioning capacity is greater than the ESE extent threshold
• 1: the percent of the available thin-provisioning capacity is greater than zero but less than or equal
to the ESE extent threshold
• 10: the percent of the available thin-provisioning capacity is zero
Note: When the size of the extent pool remains fixed or is only increased, the allocatable physical
capacity remains greater than or equal to the allocated physical capacity. However, a reduction in the size
of the extent pool can cause the allocatable physical capacity to become less than the allocated physical
capacity in some cases.
For example, if the user requests that one of the ranks in an extent pool be depopulated, the data on that
rank are moved to the remaining ranks in the pool causing the rank to become not allocated and removed
from the pool. The user is advised to inspect the limits and threshold on the extent pool following any
changes to the size of the extent pool to ensure that the specified values are still consistent with the
user’s intentions.
IBM Easy Tier
Easy Tier is an optional feature that is provided at no cost. It can greatly increase the performance of your
system by ensuring frequently accessed data is put on faster storage. Its capabilities include manual
provisioned capacity rebalance, auto performance rebalancing in both homogeneous and hybrid pools,
hot spot management, rank depopulation, manual volume migration, and thin provisioning support (ESE
volumes only). Easy Tier determines the appropriate tier of storage that is based on data access
requirements and then automatically and non-disruptively moves data, at the subvolume or sub-LUN
level, to the appropriate tier in the storage system.
Use Easy Tier to dynamically move your data to the appropriate drive tier in your storage system with its
automatic performance monitoring algorithms. You can use this feature to increase the efficiency of your
flash drives and the efficiency of all the tiers in your storage system.
You can use the features of Easy Tier between three tiers of storage within a DS8900F.
Easy Tier features help you to effectively manage your system health, storage performance, and storage
capacity automatically. Easy Tier uses system configuration and workload analysis with warm demotion
to achieve effective overall system health. Simultaneously, data promotion and auto-rebalancing address
performance while cold demotion works to address capacity.
Easy Tier data in memory persists in local storage or storage in the peer server, ensuring the Easy Tier
configurations are available at failover, cold start, or Easy Tier restart.
With Easy Tier Application, you can also assign logical volumes to a specific tier. This feature can be
useful when certain data is accessed infrequently, but needs to always be highly available.
Easy Tier Application is enhanced by two related functions:
• Easy Tier Application for IBM Z provides comprehensive data-placement management policy support
from application to storage.
• Easy Tier application controls over workload learning and data migration provides a granular pool-level
and volume-level Easy Tier control as well as volume-level tier restriction where a volume can be
excluded from the Nearline tier.
The Easy Tier Heat Map Transfer utility replicates Easy Tier primary storage workload learning results to
secondary storage sites, synchronizing performance characteristics across all storage systems. In the
event of data recovery, storage system performance is not sacrificed.
38 IBM DS8900F: DS8900F Introduction and Planning Guide