Caching temporary data in solid state storage devices
Various systems and methods for inhibiting a modified block of data from being written to an underlying persistent storage device are disclosed. A cache is maintained by a file system and the cache is implemented to temporarily cache portions of application data for an application. The application data for the application is stored on the underlying persistent storage device. Metadata is accessed if it is detected that a block of data in the cache has been modified. The metadata indicates that the block of data is not needed for the integrity of the application. In response to the metadata, the modified block of data is inhibited from being written to the underlying persistent storage device.
1. A method comprising:
detecting that a plurality of blocks of data in a cache has have been modified, wherein
the cache is maintained by a file system,
the plurality of blocks belong to a plurality of files and/or a plurality of portions of a file of the plurality of files,
the cache is implemented to temporarily cache portions of application data for an application, and
the application data for the application is stored on an underlying persistent storage device;
accessing metadata, wherein
the file system comprises the metadata,
the metadata indicates that a block of data of the plurality of blocks of data is not needed for integrity of the application, and
the integrity of the application is based, at least in part, on whether the block of data is required to restore the application; and
in response to the metadata, inhibiting the block of data from being written to the underlying persistent storage device, and writing the plurality of blocks of data, other than the block of data, to the underlying persistent storage device.
2. The method of claim 1 , wherein
the metadata in the file system comprises file system metadata and cache policy metadata, and
the file system metadata permits a cache policy of a plurality of cache policies to be applied to be modified block of data by mapping of each of one or more files of the plurality of files or each of one or more portions of the file to one of the plurality of blocks of data, based on the cache policy metadata that identifies the one or more files or the one or more portions of the one or more files that are necessary for the integrity of the application.
3. The method of claim 2 , wherein
the inhibiting comprises
accessing the file system metadata and the cache policy metadata in the file system, and
applying a first cache policy of the plurality of cache policies when the block of data is modified in the cache and the cache is implemented as a write-through cache.
4. The method of claim 2 , wherein
the inhibiting comprises
accessing the file system metadata and the cache policy metadata in the file system, and
applying a second cache policy of the plurality of cache policies when the block of data is removed from the cache and the cache is implemented as a write-through cache.
5. The method of claim 1 , wherein
the cache is implemented on a solid state drive, and
the application is a database application.
6. The method of claim 1 , comprising
detecting that a second block of data in the cache has been modified;
accessing the metadata, wherein
the metadata indicates that the second block of data is needed for the integrity of the application; and
in response to the metadata, allowing the modified block of data to be written to the underlying persistent storage device as part of the plurality of modified blocks of data.
7. The method of claim 2 , wherein
the file system metadata indicates that the block of data is part of a portion of a temporary file, and
the cache policy metadata indicates that the portion of the temporary file is not needed for the integrity of the application.
8. The method of claim 7 , wherein
the metadata identifies only a header or a tail of the temporary file are needed for the integrity of the application because the block of data is only part of the header or the tail.
9. The method of claim 1 , further comprising:
as part of the accessing,
selecting a cache policy of a plurality of cache policies from the file system; and
as part of the inhibiting,
applying the cache policy to the modified block of data.
10. A computer readable storage medium comprising program instructions executable to:
detect that a plurality of blocks of data in a cache have been modified, wherein
the cache is maintained by a file system,
the plurality of blocks belong to a plurality of files and/or a plurality of portions of a file of the plurality of files,
the cache is implemented to temporarily cache portions of application data for an application, and
the application data for the application is stored on an underlying persistent storage device;
access metadata, wherein
the file system comprises the metadata,
the metadata indicates that a block of data of the plurality of blocks of data is not needed for integrity of the application, and
the integrity of the application is based, at least in part, on whether the block of data is required to restore the application; and
in response to the metadata, inhibit the block of data from being written to the underlying persistent storage device, and write the plurality of blocks of data, other than the block of data, to the underlying persistent storage device.
11. The computer readable storage medium of claim 10 , wherein
the metadata in the file system comprises file system metadata and cache policy metadata, and
the file system metadata permits a cache policy of a plurality of cache policies to be applied to be modified block of data by mapping of each of one or more files of the plurality of files or each of one or more portions of the file to one of the plurality of blocks of data, based on the cache policy metadata that identifies the one or more files or the one or more portions of the one or more files that are necessary for the integrity of the application.
12. The computer readable storage medium of claim 11 , wherein
the inhibiting comprises
accessing the file system metadata and the cache policy metadata in the file system, and
applying a first cache policy of the plurality of cache policies when the block of data is modified in the cache and the cache is implemented as a write-through cache.
13. The computer readable storage medium of claim 10 , wherein
the cache is implemented on a solid state drive, and
the application is a database application.
14. The computer readable storage medium of claim 10 , comprising
detecting that a second block of data in the cache has been modified;
accessing the metadata, wherein
the metadata indicates that the second block of data is needed for the integrity of the application; and
in response to the metadata, allowing the modified block of data to be written to the underlying persistent storage device as part of the plurality of modified blocks of data.
15. The computer readable storage medium of claim 11 , wherein
the inhibiting comprises
accessing the file system metadata and the cache policy metadata in the file system, and
applying a second cache policy of the plurality of cache policies when the block of data is removed from the cache and the cache is implemented as a write-through cache.
16. A system comprising:
one or more processors; and
a memory coupled to the one or more processors, wherein the memory stores program instructions executable by the one or more processors to:
detect that a plurality of blocks of data in a cache have been modified, wherein
the cache is maintained by a file system,
the plurality of blocks belong to a plurality of files and/or a plurality of portions of a file of the plurality of files,
the cache is implemented to temporarily cache portions of application data for an application, and
the application data for the application is stored on an underlying persistent storage device;
access metadata, wherein
the file system comprises the metadata,
the metadata indicates that a block of data of the plurality of blocks of data is not needed for integrity of the application, and
the integrity of the application is based, at least in part, on whether the block of data is required to restore the application; and
in response to the metadata, inhibit the block of data from being written to the underlying persistent storage device, and write the plurality of blocks of data, other than the block of data, to the underlying persistent storage device.
17. The system of claim 16 , wherein
the metadata in the file system comprises file system metadata and cache policy metadata, and
the file system metadata permits a cache policy of a plurality of cache policies to be applied to be modified block of data by mapping of each of one or more files of the plurality of files or each of one or more portions of the file to one of the plurality of blocks of data, based on the cache policy metadata that identifies the one or more files or the one or more portions of the one or more files that are necessary for the integrity of the application.
18. The system of claim 16 , wherein
the cache is implemented on a solid state drive, and
the application is a database application.
19. The system of claim 16 , comprising
detecting that a second block of data in the cache has been modified;
accessing the metadata, wherein
the metadata indicates that the second block of data is needed for the integrity of the application; and
in response to the metadata, allowing the modified block of data to be written to the underlying persistent storage device as part of the plurality of modified blocks of data.
20. The system of claim 16 , wherein
the inhibiting comprises
accessing the file system metadata and the cache policy metadata in the file system; and
applying to the block,
a first cache policy of the plurality of cache policies when the block of data is modified in the cache and the cache is implemented as a write-through cache, or
a second cache policy of the plurality of cache policies when the block of data is removed from the cache and the cache is implemented as a write-back cache.
21. The system of claim 16 , wherein
the file system metadata indicates that the block of data is part of a portion of a temporary file, and
the metadata cache policy indicates that the portion of the temporary file is not needed for the integrity of the application, and
the metadata identifies only a header or a tail of the temporary file are needed for the integrity of the application because the block of data is only part of the header or the tail.