Qsan XCubeSAN XS5224D, Руководство пользователя

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Auto Tiering
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Ranking
This analysis produces a rank ordering of each sub LUN within the pool. Note that the
policies of volumes would affect how sub LUNs are ranked.
After analysis, the system would generate following information for each tier:
 The amount of data to be moved up
 The amount of data to be moved down
 The amount of data to be moved into a tier.
TIP:
The hotness analysis process which includes statistics collection and
ranking may take minutes to complete.
11.2.3. Relocation
According to the hotness analysis, relocation is processed during the user-defined
relocation window, which is the number of minutes given to the relocation process. When
the window closes, the relocation process would stop relocating data. The other parameter
is relocation rate which controls speed of the relocation process. Valid value of relocation
rate is Fast, Medium, and Slow.
Auto tiering promotes sub LUNs according to the candidate list that it created in the
analysis stage. During relocation, it prioritizes relocating sub LUNs to higher tiers. At the
same time, sub LUNs are only relocated to higher tiers if the space they occupy is required
for a higher priority. Using the mechanism, auto tiering makes sure that the higher
performing drives are always used.
During I/O, as data is written to a pool, auto tiering attempts to move it to the higher tiers if
space is available and the tiering policy allows for it. As we describe before, the relocation
process will keep 10% of the free space in all tiers. This space is reserved for any new
allocations of higher priority sub LUNs before the next relocation. Lower tiers are used for
capacity when needed. The entire relocation process is complete automatically based on
the user-defined relocation schedule, or manually if user triggers by himself. Figure 11-4
provides an illustration of how auto tiering can improve sub LUN placement in a pool.