HP StoreAll Storage - Manual (Page 226)

For a new tier, on the Manage Tier dialog box, choose Create New Tier, enter a name for the tier,
and select one or more segments to be included in the tier. To modify an existing tier, choose Use
Existing Tier, select the tier, and make any changes to the segments included in the tier.
Segments not currently included in a tier are specified as Unassigned. If you select a segment that
is already mapped to a tier, the segment will be unassigned from that tier and reassigned to the
tier you specified. If you remove a segment from a tier, that segment becomes unassigned.
226 Using data tiering