Mainframe storage apparatus that utilizes thin provisioning
View Patent ↗Each actual page inside a pool is configured from a plurality of actual tracks, and each virtual page inside a virtual volume is configured from a plurality of virtual tracks. A storage control apparatus of a mainframe system has management information that includes information denoting a track in which there exists a user record, which is a record including user data (the data used by a host apparatus of a mainframe system). Based on the management information, a controller identifies an actual page that is configured only from tracks that do not comprise the user record, and cancels the allocation of the identified actual page to the virtual page.
1. A storage apparatus coupled to a host computer, comprising:
a plurality of storage devices; and
a controller,
wherein the controller is configured to:
provide a storage pool from the plurality of storage devices, where the storage pool is comprised of a plurality of actual pages;
provide one or more virtual volumes from the storage pool to the host computer, where each of the virtual volumes is comprised of virtual pages, each of the virtual pages is comprised of virtual tracks, and each of the virtual tracks is comprised of a head and records, each of the records being configured to store user data;
when a target track of the virtual tracks in a target virtual page of the virtual pages is a target of a write access and the target virtual page has been allocated an actual page of the plurality of actual pages, determine whether or not the target track is a last track in the target virtual page;
when the target track is the last track in the target virtual page, determine whether or not the records exist in the target virtual page; and
when the records do not exist in the target virtual page, cancel the allocation of the actual page to the target virtual page,
wherein determining whether or not the target track is the last track in the target virtual page is done after the write access from the host computer to the storage apparatus.
2. The storage apparatus according to claim 1 , wherein the write access does not include a command to write user data to the records.
3. The storage apparatus according to claim 2 , wherein the write access includes a WRTRK command or an ERASE command.
4. The storage apparatus according to claim 3 ,
wherein the controller initializes the actual page, when the records do not exist in the target virtual page.
5. The storage apparatus according to claim 4 ,
wherein the storage controller further comprises a track bitmap which includes a plurality of bits indicating which of the actual pages have user data, and
wherein determining whether or not the records exist in the target virtual page includes referring to the track bitmap.
6. A method for cancelling an unnecessary actual page in a storage apparatus which is coupled to a host computer and comprises a plurality of storage devices and a controller, the method comprising the steps of:
providing a storage pool from the plurality of storage devices, where the storage pool is comprised of a plurality of actual pages;
providing one or more virtual volumes from the storage pool to the host computer, where each of the virtual volumes is comprised of virtual pages, each of the virtual pages is comprised of virtual tracks, and each of the virtual tracks is comprised of a head and records, each of the records being configured to store user data;
when a target track of the virtual tracks in a target virtual page of the virtual pages is a target of a write access and the target virtual page has been allocated an actual page of the plurality of actual pages, determining whether or not the target track is a last track in the target virtual page;
when the target track is the last track in the target virtual page, determining whether or not the records exist in the target virtual page; and
when the records do not exist in the target virtual page, cancelling the allocation of the actual page to the target virtual page,
wherein the step of determining whether or not the target track is the last track in the target virtual page is done after the write access from the host computer to the storage apparatus.
7. The method for cancelling the unnecessary actual page in a storage apparatus according to claim 6 , wherein the write access does not include a command to write user data to the records.
8. The method for cancelling the unnecessary actual page in a storage apparatus according to claim 7 , wherein the write access includes a WRTRK command or an ERASE command.
9. The method for cancelling the unnecessary actual page in a storage apparatus according to claim 8 , further comprising:
when the records do not exist in the target virtual page, initializing the actual page.
10. The method for cancelling the unnecessary actual page in a storage apparatus according to claim 9 , further comprising:
providing a track bitmap which includes a plurality of bits indicating which of the actual pages have user data,
wherein the step of determining whether or not the records exist in the target virtual page includes referring to the track bitmap.