HP XP P9500 Storage - Manual (Page 78)

Solution* When tier relocation is canceled
Collect monitoring information again. Collected monitoring information is discarded (see “Collected
monitoring information is discarded” (page 77) .
Because the tier relocation in the next cycle is started
automatically, an action for this problem is unnecessary. The execution mode is Auto, and the tier relocation is not
completed in an execution cycle.
Continue monitoring and issue a monitor stop, followed
by a relocation start. The execution mode is Manual and relocation is stopped.
Notes:
1. If the execution mode is Auto, or if you use scripts in the Manual execution mode, monitoring information will be
collected automatically at the next execution cycle, and then relocation will be performed.
2. If the monitoring information about the corresponding volume is discarded, the relocation of the volume is canceled.
Buffer area of a tier
Smart Tiers uses buffer percentages to reserve pages for new page assignments and allow the tier
relocation process. Areas necessary for processing these operations are distributed corresponding
to settings used bySmart Tiers. The following describes how processing takes place to handle the
buffer percentages.
Reserved pages for relocation operation: A small percentage of pages are reserved per tier to
allow relocation to operate. These are the buffer spaces for tier relocation
New page assignment: New pages are first assigned from the top most tier within available pages.
New page allocation avoids using a page reserved for the buffer area for tier relocation. If there
are no other pages available, the new page relocation will use any free page. The buffer area for
new page relocation can be set to improve the availability of free pages in upper tiers.
Tier relocation workflow: Tier relocation is performed usingtaking advantage of the buffer space
allocated for tier relocation, as mentioned above. Each tier may temporarily be assigned to over
98% of capacity.Tier relocation is also performed to secure the space ofreserved in each tier for
anew page assignment, which is assigned after tier relocation.assignment. The area is called the
buffer space for new page assignments. When tier relocation is performed, Smart Tiers reserves
buffer spaces for relocation and new page assignment.
During relocation, a tier may temporarily be assigned over 98% of capacity as well, or well under
the allowance for the buffer areas.
Buffer space: The following table shows the default rates (rate to capacity of a tier) of buffer space
used for tier relocation and new page assignments, listed by drive type. The default values can be
changed, if needed, using Storage Navigator or RAID Manager.
Total buffer area for new page
assignment buffer area for tier relocation Drive type
2% 0% 2% SSD
10% 8% 2% Non-SSD 15K rpm
Further influence on tier relocation and tier occupancy: The buffer area for tier relocation and new
page assignment will influence the amount that a tier’s capacity is used. Two other aspects will
influence the amount of tier used:
1. If a tier’s performance limit is high, then Smart Tiers may increase the amount of a tier that is
not used.
2. If the relocation cycle’s duration is not long enough for the allocation moves to all complete,
then the amount of tier capacity used may not fully represent the desired target levels.
Subsequent relocations should eventually reach the target levels.
78 Configuring thin provisioning