Dear all,
I have some problems with zfs implementation issues:
I do not really understand what is a DSL directory (I though is was kind
of structure listing all datasets + properties..) and what is the unique
"Active Dataset" within a DSL directory?
To make it clearer , let''s say that I have a pool named mypool with two
FSs fs1 & fs2 , each of them with several clones/snapshots, what will be
the relatec DSL directory(ies?) and corresponding active datasets?
According
http://opensolaris.org/os/community/zfs/docs/ondiskformat0822.pdf , the
following path has to be taken to reach a file from uberblock
uberblock->MOS->root_dataset->DSL object directory -> DSL (active
one as I
understand) ->FS->...->file
How to get to a non active dataset ? DSL object directory links to DSL
through dd_head_dataset_object , i do not see any other possible links in
dsl_dir_phys structure?
I think that those 2 questions are 2 different faces of the same coin.
Cheers
C Rouhassia
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Cyril ROUHASSIA wrote:> > Dear all, > I have some problems with zfs implementation issues: > > * I do not really understand what is a DSL directory (I though is > was kind of structure listing all datasets + properties..) and > what is the unique "Active Dataset" within a DSL directory?Yes, the DSL directory (dsl_dir_[phys_]t structures) keeps track of the naming hierarchy of datasets (eg, the fact that under "pool" there are filesytems "fs1" and "fs2" -- in dd_child_dir_zapobj). It also keeps track of properties that use the generic dsl_prop_* infrastructure (in dd_props_zapobj), quota and reservation, and space usage information (aggregating space used by children as well). You can find more details in the structure definitions in dsl_dir.h. The "active dataset" means the non-snapshot dataset, which can be modified. It is dd_head_dataset_obj. The active dataset (synonymous with head dataset) has the list of snapshots (ds_snapnames_zapobj). Note that a clone is not really different than any other filesystem from the dsl_dataset point of view (actually, it is barely different from any implementation point of view). Eg, a clone has a head/active dataset and may have snapshots, children datasets, etc. Hope that helps. --matt> ************************************************************************* > This message and any attachments (the "message") are confidential, intended solely for the addressee(s), and may contain legally privileged information.Then maybe you shouldn''t be posting it on a public mailing list :-\