System and method to guarantee overwrite of expired data in a virtual tape server

#1. Field of the Invention

#This invention relates generally to automated data storage systems, and particularly, to novel improvements in virtual tape server subsystems for ensuring that expired data is overwritten within a time interval set by a user.

#2. Discussion of the Prior Art

#Further features, aspects and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and the accompanying drawings where:

#FIG. 1 illustrates is a block diagram illustrating the physical hardware components comprising the VTS 100 according to the prior art.

#FIG. 2 illustrates the relationship between several virtual and real image of components according to the prior art.

#The requirement that the old version(s) of the VTS volume must be handled to guarantee that they cannot be recovered is met by overwriting a physical volume that contains invalidated virtual volume data within a time interval specified by the customer.

#Thus, there is introduced a function, implemented by the VTS, and particularly, the storage management software component of the VTS, for enabling data associated with a virtual (logic) volume to be invalidated.

#In the context of the invention, there is defined an aggregation or group of physical volumes in a VTS that comprise a “pool”, with each physical volume including one or more logical (virtual) volumes. Pooling concepts are well known in the industry with IBM's Tivoli Storage Manager being an exemplary system implementing such volume pool concepts. FIG. 3(a) illustrates a pool set-up table 20 comprising data for the VTS system indicating how the physical volumes may be organized. As shown in FIG. 3(a), each of the physical volumes managed by the VTS system is assigned to a pool, with the table 20 indicating 32 pools, for example. It is understood that each pool 25 of physical volumes is assigned a name and may have one or more parameters 30 associated therewith. For example, typical parameters associated with a pool include, but are not limited to: a media type (e.g., physical volumes having 10 Gbyte tape or 20 Gbyte tape); a rule(s) for managing volumes in a pool. One rule may involve the concept of “reclamation” whereby the VTS tracks what percentage of data associated in a particular physical volume is still valid. That is, over time, data space occupied by a logical volume needs to be reclaimed from a physical volume when it is no longer used or needed by the host, i.e., has expired. Thus, in the pooling table, a reclamation threshold parameter may be set to indicate what percentage of data on the volume is still active. Thus, if any volume(s) in the pool falls below that reclaim percent threshold, then a reclamation process will be performed to take the valid logical volume(s) off of the physical volume and put it on another physical volume—potentially combining multiple partially full physical volumes and filling up the other. The percentage at which a volume is reclaimed is another useful parameter defining the pool.