100 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
Throttles for pools
Throttling is a mechanism to control the amount of resources that are used when the system
is processing I/Os on a specific pool. If a throttle is defined, the system either processes the
I/O, or delays the processing of the I/O to free resources for more critical I/O. The system also
supports throttles to delay processing of I/O operations for pools. If storage systems provide
storage to a wide variety of applications, then production pools with more critical I/O can be
competing with pools that have lower priority operations.
For example, pools that are used for backup or archive operations can have I/O intensive
workloads, potentially taking bandwidth from production pools. Pool throttles can be used to
limit I/Os for these types of pools so that I/O operations for production pools are not affected.
Figure 3-39 shows an example of pool throttling.
Figure 3-39 Pool throttling
Limits of the throttles are shown in Figure 3-40.
Figure 3-40 Throttling limits
3.4.2 Child pools
Before V7.4, the disk space of a storage pool was provided from MDisks, so the capacity of a
storage pool depended on the MDisks’ capacity. Creating or splitting a storage pool is
impossible. A user cannot create a storage pool and specify the capacity that they want.
A
child pool is a new logical object that is created from a physical storage pool. A child pool
provides most of the functions that pools offer (for example, volume creation), but the user
can specify the capacity of the child pool at creation. Administrators can use child pools to
control capacity allocation for volumes that are used for specific purposes.
IOPS limit
Bandwidth limit
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