In one aspect of the present description, a data preservation function is provided for preserving a set of data on a source storage device at a point in time, and includes identifying as a function of prior update usage, such as input/output usage, of the data to be preserved, a portion of the data which is more likely to be the subject of updates during at least a portion of the data preservation operation as compared to the remaining portion of the data to be preserved, and copies the identified portion of the data to be preserved to a target storage device. In another aspect, the size of the portion of data to be identified is variable. Other features and aspects may be realized, depending upon the particular application.