Hi,

 From the recent SOC discussion I gather that the advantage of 
journalling over softdep is the fast replay of the journal obviating the 
need to fsck the whole disk. My thinking here is that softdep and 
journalling has been kept as independent strategies and that a combined 
softdep+journal may prove slightly simpler and more efficient than a 
full blown independent journal solution.

since softdep ensures the safety of the data on disk, would it not be 
possible to create a softdep journal that logs enough detail to identify 
just those areas of disk that would need to an fsck? That is after all 
the purpose of a normal journal, to identify those parts of the disc 
that need updating/fixing. softdep ensures that we don't need to log how 
to fix it, just what needs fixing.

my other thought on the matter is that softdep reduces the number of 
writes to disk by delaying the writes for a short time and optimising 
the write dependency graph, it then has the expense of rollbacks to 
ensure consistency. could not a journal take the place of the rollbacks 
allowing fast sequential writes of the rollback data?

Simon