cvs commit: src/sys/vfs/hammer hammer.h hammer_disk.h hammer_io.c hammer_ondisk.c
dillon at apollo.backplane.com
Fri Aug 29 14:52:21 PDT 2008
:What's the status of UFS with soft updates with respect to disk cache
:flushing? Doesn't do it currently and therefore can't provide its
:guarantees for consistency after a power failure?
It's almost impossible to do with UFS unless you want to slow
performance to a crawl. While softupdates can gang unrelated writes
together, it can't gang dependant writes together at all so each
element in a dependancy chain would require its own flush command.
HAMMER dependancies work differently. HAMMER dependancies can be
ganged together into two groups of writes, typically requiring only
two flush commands to clean out the entire buffer cache.
<dillon at backplane.com>
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