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This is what HP Support provided me on how AO works:
Setting mode as Performance will move as much data as possible to higher tiers but it does not mean that data will not be moved to lower tiers.
In your case, we see the AO is working as per design, even in idlest Performance and zero performance also data is not getting moved to lower tier it means that there are no idle data or zero performance data which can be moved to lower tiers.
I have also explained below how AO is designed to work for your better understanding. AO uses certain algorithms to decide the region moves between the tiers. All listed below.
The AO moves the regions between tiers based on certain algorithm. It uses below 3 algorithm to move data between tiers.
1. Space available in the tiers.
In this, If the space in a tier exceeds the tier size (or the CPG warning limit), then the algorithm will first try to move regions out of that tier into any other tier with available space in an attempt to lower the tier’s size below the limit. If no other region has space, then the algorithm logs a warning and does nothing. (Note that if the warning limit for any CPG is exceeded, the array will generate an alert.) If space is available in a faster tier, it chooses the busiest regions to move to that tier. Similarly, if space is available in a slower tier, it chooses the most idle regions to move to that tier. The average tier service times and average tier access rates are ignored when data is being moved because the size limits of a tier have been exceeded
2. Average tier service times.
Normally, HP 3PAR Adaptive Optimization tries to move busier regions in a slow tier into higher performance tiers. However, if a higher performance tier gets overloaded (too busy), performance for regions in that tier may actually be lower than regions in a “slower” tier. In order to prevent this, the algorithm does not move any regions from a slower to a faster tier if the faster tier’s average service time is not lower than the slower tier’s average service time by a certain factor (a parameter called svctFactor). There is an important exception to this rule because service times are only significant if there is sufficient IOPS load on the tier. If the IOPS load on the destination tier is below another value (a parameter called minDstIops), then we do not compare the destination tier’s average service time with the source tier’s average service time. Instead, we use an absolute threshold (a parameter called maxSvctms).
3. Average tier access densities.
When not limited, as described above, by lack of space in tiers or by high average tier service times, adaptive optimization computes the average tier access rate densities (a measure of how busy the regions in a tier are on average, calculated with units of IOPS per gigabyte per minute) and compares them with the access rate densities of individual regions in each tier. Then, it decides whether to move the region to a faster or slower tier.
We first consider the algorithm for selecting regions to move from a slower to a faster tier. For a region to be considered busy enough to move from a slower to a faster tier, its access rate density and accr(region) must satisfy these two conditions:
1. First, the region must be sufficiently busy compared to other regions in the source tier:
accr(region) > srcAvgFactorUp(Mode) * accr(srcTier) Where accr(srcTier) is the average access rate density of the source (slower) tier and srcAvgFactorUp(Mode) is a tuning parameter that depends on the mode configuration parameter. Note that by selecting different values of srcAvgFactorUp for performance, balanced or cost mode values HP 3PAR Adaptive Optimization can control how aggressive the algorithm is in moving regions up to faster tiers.
2. Second, the region must meet one of two conditions: It must be sufficiently busy compared with other regions in the destination tier, or it must be exceptionally busy compared with the source tier regions. This second condition is added to cover the case in which a very small number of extremely busy regions are moved to the fast tier, but then the average access rate density of the fast tier create too high a barrier for other busy regions to move to the fast tier:
accr(region) > minimum((dstAvgFactorUp(Mode) * accr(dstTier)), (dstAvgMaxUp(Mode) * accr(srcTier)))
The algorithm for moving idle regions down from faster to slower tiers is similar in spirit—but instead of checking for access rate densities greater than some value, the algorithm checks for access rate densities less than some value:
accr(region) < srcAvgFactorDown(Mode) * accr(srcTier) and
accr(region) < maximum((dstAvgFactorDown(Mode) * accr(dstTier)), (dstAvgMinDown(Mode) * accr(srcTier)))
HP makes a special case for regions that are completely idle (accr(region) = 0). These regions are moved directly to the lowest tier.
AO uses all the algorithms when performing the moves. Whichever algorithm suites best, it choses that mechanism to decide the movements. The Space algorithm will be considered only when there is a space crunch. The rest of the algorithms will be used every time the AO runs. In your case except the space algorithm, rest all algorithms will be used to decide the movements.
Note : AO Metrics are purely depends on your AO setup Environment and configuration. There will not be any fixed or defined values for metrics, its changes as per your AO setup.
These are internal to the AO software and can’t be set by user. The Inserv will decide all these parameters based on the sample collection. It varies depending upon the load on the inserv and the physical disks.
With Inform OS 3.1.1 or earlier, in a given schedule, AO can move only 1TB of data between tiers. With on Node AO you can move more than 1 TiB or 5% of total AO config capacity. However, without looking to the AO config we cannot decide hence the statement as the warnings may be set at CPG level and we all know that AO respects the warning or limit set at AO CPG.
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