Techniques for storing metadata of a filesystem in persistent memory

摘要

A method is presented for operating a filesystem. The method includes (a) storing data of the filesystem in a data storage filesystem (DSFS) in block-addressable non-volatile storage and (b) storing metadata of the filesystem in a metadata filesystem (MDFS) separate from the DSFS, at least a portion of the metadata being stored in word-addressable memory (WAM) having a persistence feature. Several embodiments are described for achieving this, using, for example, only non-volatile WAM, while other embodiments are described using, for example, a combination of volatile WAM and persistence techniques, while yet other embodiments are described using, for example, a combination of persistence-enhanced WAM and data storage.

主权项

1. A method of operating a data storage system having a filesystem, the data storage system being configured to efficiently process received read and write commands directed at the filesystem, the method comprising:
storing data of the filesystem in a data storage filesystem (DSFS) in block-addressable non-volatile storage; storing metadata of the filesystem in a metadata filesystem (MDFS) separate from the DSFS, at least a portion of the metadata being stored in word-addressable memory (WAM) having a persistence feature, wherein storing the metadata of the filesystem in the MDFS separate from the DSFS, at least a portion of the metadata being stored in WAM having the persistence feature includes:
storing all of the metadata of the filesystem within volatile random access memory (RAM);storing descriptors of changes made to the metadata within a non-volatile log as the changes are made;periodically copying the metadata from the volatile RAM onto block-addressable non-volatile storage as a snapshot; andupon copying the metadata from the volatile RAM onto block-addressable non-volatile storage as the snapshot, clearing the non-volatile log; and upon a system failure:
loading the snapshot from the block-addressable non-volatile storage onto the volatile RAM, thereby recreating a version of the MDFS within the volatile RAM;applying the changes stored within the non-volatile log to the version of the MDFS within the volatile RAM, thereby creating an up-to-date version of the MDFS within the volatile RAM; andsubsequent to creating the up-to-date version of the MDFS within the volatile RAM:
clearing the non-volatile log; andresuming normal operation of the filesystem.