Snapshot cauterization
Implementations disclosed herein provide for cauterizing portions of a snapshot. A file and/or directory or a set of files and directories of a snapshot can be identified via a user request or an automated process for cauterization. When cauterized, if a previous snapshot does not contain a ditto entry to the portion of the current snapshot that is requested to be cauterized, the BADDR associated with the cauterized portion of the snapshot can be freed for other storage use. In some implementations, metadata associated with the data that is cauterized can be retained for other uses.
1. A method comprising:
receiving a request to cauterize a portion of a snapshot, wherein the request includes a set of cauterized items, wherein a cauterized item in the set of cauterized items are at least one of a file or a directory, and wherein cauterizing the portion of the snapshot does not delete the snapshot; and
cauterizing the portion of the snapshot by iteratively, for cauterized items in the set of cauterized items:
determining whether a previous snapshot is associated with the cauterized item;
in response to determining that that a previous snapshot is not associated with the cauterized item, freeing a block address associated with the cauterized item for other use;
in response to determining that that a previous snapshot is associated with the cauterized item, determining whether a ditto record is associated with the cauterized item within the previous snapshot;
in response to determining that a ditto record is not associated with the cauterized item within the previous snapshot, freeing a block address associated with the cauterized item for other use; and
in response to determining that a ditto record is associated with the cauterized item within previous snapshot, modifying the ditto record within the previous snapshot to indicate that the block address associated with the cauterized item is being retained by the previous snapshot.
2. The method of claim 1 , further comprising:
in response to freeing the block address associated with the cauterized item for other use, retaining metadata associated with the cauterized item.
3. The method of claim 1 , further comprising:
modifying a snapshot tracking file, an inode, and a metatree associated with the snapshot based on the request.
4. The method of claim 1 , further comprising:
estimating an amount of space that can be freed based on the request.
5. A system comprising for protecting data, comprising at least one storage device and at least one processor configured to:
receive a request to cauterize a portion of a snapshot, wherein the request includes a set of cauterized items, wherein a cauterized item in the set of cauterized items are at least one of a file or a directory, and wherein cauterizing the portion of the snapshot does not delete the snapshot; and
cauterize the portion of the snapshot by iteratively, for cauterized items in the set of cauterized items:
determine whether a previous snapshot is associated with the cauterized item;
in response to determining that that a previous snapshot is not associated with the cauterized item, free a block address associated with the cauterized item for other use;
in response to determining that that a previous snapshot is associated with the cauterized item, determine whether a ditto record is associated with the cauterized item within the previous snapshot;
in response to determining that a ditto record is not associated with the cauterized item within the previous snapshot, free a block address associated with the cauterized item for other use; and
in response to determining that a ditto record is associated with the cauterized item within previous snapshot, modify the ditto record within the previous snapshot to indicate that the block address associated with the cauterized item is being retained by the previous snapshot.
6. The system of claim 5 , further configured to:
in response to freeing the block address associated with the cauterized item for other use, retain metadata associated with the cauterized item.
7. The system of claim 5 , further configured to:
modify a snapshot tracking file, an inode, and a metatree associated with the snapshot based on the request.
8. The system of claim 5 , further configured to:
estimate an amount of space that can be freed based on the request.
9. A computer readable medium with program instructions stored thereon to perform the following acts:
receiving a request to cauterize a portion of a snapshot, wherein the request includes a set of cauterized items, wherein a cauterized item in the set of cauterized items are at least one of a file or a directory, and wherein cauterizing the portion of the snapshot does not delete the snapshot; and
cauterizing the portion of the snapshot by iteratively, for cauterized items in the set of cauterized items:
determining whether a previous snapshot is associated with the cauterized item;
in response to determining that that a previous snapshot is not associated with the cauterized item, freeing a block address associated with the cauterized item for other use;
in response to determining that that a previous snapshot is associated with the cauterized item, determining whether a ditto record is associated with the cauterized item within the previous snapshot;
in response to determining that a ditto record is not associated with the cauterized item within the previous snapshot, freeing a block address associated with the cauterized item for other use; and
in response to determining that a ditto record is associated with the cauterized item within previous snapshot, modifying the ditto record within the previous snapshot to indicate that the block address associated with the cauterized item is being retained by the previous snapshot.
10. The computer readable medium of claim 9 , further comprising:
in response to freeing the block address associated with the cauterized item for other use, retaining metadata associated with the cauterized item.
11. The computer readable medium of claim 9 , further comprising:
modifying a snapshot tracking file, an inode, and a metatree associated with the snapshot based on the request.
12. The computer readable medium of claim 9 , further comprising:
estimating an amount of space that can be freed based on the request.