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When salvaging a volume (with DAFS or not), it is required to read the volume headers of all volumes on the partition, so we know what volumes are in the same volume group as the salvaged volume. Currently with DAFS, this requirement can make demand-salvages very slow, since each demand-salvage must read each volume header on the partition. So, instead of having each demand-salvage read the volume headers itself, have a demand-salvage request the required volume group hierarchy information from the fileserver. The fileserver will scan the partition's volume headers, and will keep the hierarchy cached in memory. Any modifications to this hierarchy from volume creation/deletion will update this volume group cache (VGC) via FSSYNC commands. This results in a dramatic salvaging speedup when many demand-salvages are requested, and eliminates the cases where DAFS salvaging can be significantly slower than non-DAFS salvaging. FIXES 124488 Change-Id: Ie9ae655593ad8a90ca6ad8f63e6b6e799f283988 Reviewed-on: http://gerrit.openafs.org/880 Reviewed-by: Derrick Brashear <shadow@dementia.org> Tested-by: Derrick Brashear <shadow@dementia.org> |
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| .. | ||
| arch-overview.h | ||
| dafs-fsa.dot | ||
| dafs-vnode-fsa.dot | ||
| fssync.txt | ||
| README | ||
- dafs-fsa.dot is a description of the finite-state machine for volume
states in the Demand Attach fileserver
- dafs-vnode-fsa.dot is a description of the finite-state machine
for vnodes in the Demand Attach fileserver.
Both diagrams are in Dot (http://www.graphviz.org) format,
and can be converted to graphics formats via an
an invocation like:
dot -Tsvg dafs-fsa.dot > dafs-fsa.svg