Abstract: Each node in a clustered array is the owner of a set of zero logical disks (LDs). Thinly-provisioned VVs (TPVVs) are partitioned so each is mapped to a group of zero LDs from different sets of zero LDs. When there is a change in ownership, the affected zero LDs are switched one at a time so only a group of the TPVVs is affected each time.

Abstract: Methods are provided to write zeroes to logical blocks of a thin-provisioned volume mapped to a deleted file or a dummy file in the host file system. This causes the thin-provisioned volume to map these logical blocks to a common storage space that contains all zeroes so that storage space previously mapped to these logical blocks is free to be reused.

Abstract: Each node in a clustered array is the owner of a set of zero logical disks (LDs). Thinly-provisioned VVs (TPVVs) are partitioned so each is mapped to a group of zero LDs from different sets of zero LDs. When there is a change in ownership, the affected zero LDs are switched one at a time so only a group of the TPVVs is affected each time.

Abstract: A chain of snapshots includes a more recent snapshot with a data block copied from a base volume, a less recent snapshot with a skip-pointer that leads to the data block in said more recent snapshot, and one or more intermediate snapshots between the more recent snapshot and the less recent snapshot in the chain of snapshots.

Abstract: A snapshot tree structure includes a base volume storing a current user data at a current time, a first read-only snapshot descending from the base volume, and a second read-only snapshot descending from the first read-only snapshot. The first read-only snapshot is created at a first time earlier than the current time. The first read-only snapshot stores a first data of the base volume at the first time before the first data is modified in the base volume. The second read-only snapshot is created at a second time earlier than the first time. The second read-only snapshot stores a second data of the base volume at the second time before the second data is modified in the base volume.

Abstract: A snapshot tree structure includes a base volume storing a current user data, a first snapshot descending from the base volume, and a second snapshot descending from the first snapshot, wherein the second snapshot was created prior to the first snapshot. The first snapshot includes a first table corresponding to first portions of block addresses, a second table corresponding to second portions of the block addresses, and a third table to third portions of the block addresses. The first table includes an entry with a pointer to the second table. The second table includes an entry with a pointer to the third table. The third table includes an entry with a pointer to a data of the base volume before the data is modified in the base volume.

Abstract: A chain of snapshots includes read-write snapshots descending from a read only snapshot. The read only snapshots presents a constant view of the data at the time the read only snapshot is created, and the read-write snapshot starts with the view but can be modified by the user without changing the view of its parent snapshot (e.g., the read only snapshot). Accordingly, the read-write snapshot can be written for various testing purposes while the read only snapshot remains undisturbed to preserve the original data.