Metadata management

摘要

In one embodiment, a copy relationship is established between a storage location at a first site and a storage location at a second site, in a manner which includes selectively either 1) synchronously writing a modified metadata track from a cache to data storage if the metadata track in cache is a mixture of ones and zeros, before staging from data storage into the cache, the next track of the sequence of tracks of metadata, or 2) instead of synchronously writing from cache the modified metadata track, entering a journal entry to protect the modified metadata track in cache if the metadata track in cache is one of all ones and all zeros, so that asynchronous writing of the modified metadata track from cache is substituted for synchronous writing from cache. Other aspects are described.

主权项

1. A method, comprising:
sequentially processing a plurality of tracks of metadata in sequence wherein each metadata track is metadata for a plurality of tracks of a source volume wherein the sequential metadata processing includes for each metadata track: staging from data storage into a cache, a track of the sequence of tracks of metadata; modifying the metadata track in cache; and before staging from data storage the next track of the sequence of tracks of metadata into the cache, selectively either 1) synchronously writing the modified metadata track from the cache to data storage if the metadata track in cache is a mixture of ones and zeros, or 2) instead of synchronously writing from cache the modified metadata track, entering a journal entry to protect the modified metadata track in cache if the metadata track in cache is one of all ones and all zeros, so that synchronous writing of the modified metadata track from cache is omitted.