DATA STORAGE SPACE RECOVERY SYSTEM AND METHOD

• US 20080320061A1
• Filed: 06/22/2007
• Published: 12/25/2008
• Est. Priority Date: 06/22/2007
• Status: Active Grant

• Current Assignee: Dell International LLC (Dell Technologies Inc.)
• Original Assignee: Compellent Technologies Incorporated (Dell Technologies Inc.)
• Inventors: Klemm, Michael J., Aszmann, Lawrence E., Pittelko, Michael H., Olson, Mark D.
• Granted Patent: US 8,601,035 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0223 User address space allocation, e.g. contiguous or non contiguous base addressing
• CPC Class Codes: G06F 16/1727 Details of free space management performed by the file system saving storage space on storage systems G06F3/0608; management of blocks in storage devices G06F3/064
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0671 In-line storage system
• CPC Class Codes: G06F 3/0676 Magnetic disk device

Abstract

A process of determining explicitly free data space in computer data storage systems with implicitly allocated data space through the use of information provided by a hosting computer system with knowledge of what space allocated is currently being used at the time of a query, is provided. In one embodiment, a File System (“FS”) is asked to identify clusters no longer in use which is then mapped to physical disks as visible to an Operating System (“OS”). The physical disks are mapped to simulated/virtualized volumes presented by a storage subsystem. By using server information regarding the FS, for those pages that are no longer in use, point in time copy (“PITC”) pages are marked for future PITC and will not be coalesced forward, thereby saving significant storage.

Claims

1. A process of determining explicitly free data space in computer data storage system, comprising the steps of:

inquiring what space allocated is in use and not in use;

providing implicitly allocated data space through use of information provided by a hosting computer system; and

mapping the space allocated from physical disks, to virtual volumes, and to point in time copy (“

PITC”

) pages, wherein space no longer in use are identified in PITC pages and will not be coalesced forward and freed in a pagepool list.

2. A process of determining explicitly free data space in a computer data storage system with implicitly allocated data space, comprising the steps of:

identifying file system (“

FS”

) allocation units/sectors/clusters, wherein the FS allocation units/sectors/clusters are allocated and mapped with operating system (“

OS”

) physical disk units/sectors;

transporting an unused block list of explicitly free areas to a storage subsystem;

trimming the unused block list of explicitly free areas to only include full pages in the storage subsystem;

determining whether each block in the unused block list is in an active point-in-time copy (“

PITC”

) or a historical PITC, wherein the active PITC is a storage area or page that has been used and is not in use, whereas the historical PITC is a storage area or page that has been used and will potentially be freed when the active PITC expires, wherein,

if the block in the unused block list is the active PITC, then returning the page to a free list; and

if the block in the unused block list is a historical PITC, marking the page in the active PITC as available to be freed when the PITC owning the corresponding pages is expired.

3. The process of claim 2, further comprising the step of modifying the active PITC which tracks changes to a volume of virtual storage space for a given time period.