Abstract: Systems and methods of performing a host write process are provided. W blocks are selected from the multiple blocks and W is a natural number. Write target data in accordance with a write command is written to the W next write destination pages which are included in the W blocks respectively. Each block selected is a block whose next write destination page is a first kind page. Each block consists of multiple pages. The multiple pages are two or more first kind pages and two or more second kind pages. Each second kind page is a page with a lower write performance than that of each first kind page.

Abstract: A virtual computer system having a plurality of virtual computers includes an area assignment unit operable to, when a virtual computer attempts to perform writing to a basic area which is assigned to and shared by the plurality of virtual computers, change an assignment to the virtual computer from the basic area to a copy area to which the basic area is copied and the writing is performed. Additionally an area freeing unit is operable to, when a content of the basic area matches a content of at least one copy area, change area assignment to one or more virtual computers, to which have been assigned one or more other areas than one area among the areas whose contents match each other, to the one area, and free the one or more other areas.

Abstract: Various embodiments for improving data storage and retrieval performance, for a tiered storage environment having levels corresponding to storage performance, are provided. In one embodiment, by way of example only, reference count information of at least one data segment maintained in the tiered storage environment is used to determine which of the levels in the tiered storage environment the at least one data segment will be assigned. Those of the at least one data segment having higher reference counts are assigned to a higher performance level than those having lower reference counts.

Abstract: Various embodiments for improving data storage and retrieval performance, for a tiered storage environment having levels corresponding to storage performance, are provided. In one embodiment, by way of example only, reference count information of at least one data segment maintained in the tiered storage environment is used to determine which of the levels in the tiered storage environment the at least one data segment will be assigned. Those of the at least one data segment having higher reference counts are assigned to a higher performance level than those having lower reference counts.