3PAR System Reporter User’s Guide | System Reporter 2.8 |
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9.3.1Tier Definition (CPG Name and GiB)
Each tier is defined by the CPG and the maximum space that the tier should use. The CPG definition includes all the parameters necessary to define a storage tier’s quality of service: the disk type, disk speed, RAID type, etc. You can specify either two or three tiers. When you specify two tiers you can choose which tier to leave out by setting its CPG to
NOTE: When you specify two tiers, for the purposes of analysis and data movement only the order of the tiers matters, not the actual tier number. For example specifying tiers 0 and 1 is equivalent to specifying 0 and 2 or 1 and 2. The lower numbered tier is considered the faster tier and the higher numbered tier is considered the slower tier.
However, you should consider whether you may want to add a tier in the future, and if so what tier number that is likely to be, and leave out that tier number for the two tier configuration. For example, if you have SSD PDs and NL PDs, you may want to use SSD PDs for the tier 0 CPG, NL PDs for the tier 2 CPG, and leave tier 1 empty for the possibility of a CPG using FC PDs.
The maximum space in GiB for the tier allows you to limit how much space in a tier is available for a given configuration. If you do not want to place a limit on the amount of space for a tier, you can enter a large value that is unlikely to be exceeded.
Adaptive Optimization looks at several limits on the CPG:
■The CPG allocation (hard) limit
■The CPG warning limit
■The AO space limit for the tier
Adaptive Optimization takes the minimum of these limits and treats that as a space limit for the CPG and attempts to keep the total LD used space in the CPG below this limit (by a margin of about two times the grow size of the CPG).
9.6 | Configuring Adaptive Optimization |