Identifying allocated blocks in a storage system
Techniques are used for identifying allocated blocks in a storage system. The techniques may be used to provide, among other things, retrieval of a value associated with a most recent reinitialization of the storage system. For a tier of user data storage in the storage system, a page of storage with the value and a marker indicating that the page marks an end of storage that has been allocated for the tier of user data storage may be identified. Storage may be allocated from a page immediately preceding the identified page.
1. A method comprising:
retrieving a value associated with a most recent reinitialization of the storage system;
identifying, for a tier of user data storage in the storage system, a page of storage with the value and a marker indicating that the page marks an end of storage that has been allocated for the tier of user data storage; and
allocating storage from a page immediately preceding the identified page.
2. The method of claim 1 , wherein retrieving the value associated with the most recent reinitialization of the storage system comprises:
retrieving a timestamp.
3. The method of claim 1 , wherein identifying the page of storage with the value and the marker comprises:
determining an anchor page for the tier of user data storage;
retrieving, from the anchor page, a pointer to a page;
verifying whether the page associated with the pointer includes the value and the marker.
4. The method of claim 3 , wherein determining the anchor page for the tier of user data storage comprises:
accessing a superblock associated with the tier of user data storage to retrieve a pointer to an anchor page.
5. The method of claim 3 , further comprising:
upon determining that the page associated with the pointer from the anchor page does not include the value or the marker, searching for a page that does include the timestamp and the marker.
6. The method of claim 1 , further comprising:
determining that all of the storage on the page immediately preceding the identified page has been allocated;
writing the value and the marker to the page immediately succeeding the identified page; and
allocating storage from the identified page.
7. The method of claim 6 , wherein allocating storage from the identified page comprises:
overwriting the value and the marker on the identified page with structures for the map.
8. The method of claim 1 , further comprising:
reinitializing the storage system;
storing, for each tier of user data storage, a value associated with the reinitialization of the storage system in a superblock, an anchor page, and a page with the marker.
9. A system comprising at least one processor configured to:
retrieve a value associated with a most recent reinitialization of the storage system;
identify, for a tier of user data storage in the storage system, a page of storage with the value and a marker indicating that the page marks an end of storage that has been allocated for the tier of user data storage; and
allocate storage from a page immediately preceding the identified page.
10. The system of claim 9 , wherein the processor is further configured to:
retrieve a timestamp.
11. The system of claim 9 , wherein the processor is further configured to:
determine an anchor page for the tier of user data storage;
retrieve, from the anchor page, a pointer to a page;
verify whether the page associated with the pointer includes the value and the marker.
12. The system of claim 11 , wherein the processor is further configured to:
access a superblock associated with the tier of user data storage to retrieve a pointer to an anchor page.
13. The system of claim 11 , wherein the processor is further configured to:
upon determining that the page associated with the pointer from the anchor page does not include the value or the marker, search for a page that does include the timestamp and the marker.
14. The system of claim 9 , wherein the processor is further configured to:
determine that all of the storage on the page immediately preceding the identified page has been allocated;
write the value and the marker to the page immediately succeeding the identified page; and
allocate storage from the identified page.
15. The system of claim 14 , wherein the processor is further configured to:
overwrite the value and the marker on the identified page with structures for the map.
16. The system of claim 9 , wherein the processor is further configured to:
reinitialize the storage system;
store, for each tier of user data storage, a value associated with the reinitialization of the storage system in a superblock, an anchor page, and a page with the marker.