> [EMAIL PROTECTED] wrote: > > Darren, > > > > Do you happen to have any links for this? I > have not seen anything > > about NTFS and CAS/dedupe besides some of the third > party apps/services > > that just use NTFS as their backing store. > > Single Instance Storage is what Microsoft uses to > refer to this: > > http://research.microsoft.com/sn/Farsite/WSS2000.pdf
While SIS is likely useful in certain environments, it is actually layered on top of NTFS rather than part of it - and in fact could in principle be layered on top of just about any underlying file system in any OS that supported layered 'filter' drivers. File access to a shared file via SIS runs through an additional phase of directory look-up similar to that involved in following a symbolic link, and its described copy-on-close semantics require divided data access within the updater's version of the file (fetching unchanged data from the shared copy and changed data from the to-be-fleshed-out-after-close copy) with apparently no mechanism to avoid the need to copy the entire file after close even if only a single byte within it has been changed (which could compromise its applicability in some environments). Nonetheless, unlike most dedupe products it does apply to on-line rather than backup storage, and Microsoft deserves credit for fielding it well in advance of the dedupe startups: once in a while they actually do produce something that qualifies as at least moderately innovative. NTFS was at least respectable if not ground-breaking as well when it first appeared, and it's too bad that it has largely stagnated since while MS pursued its 'structured storage' and similar dreams (one might suspect in part to try to create a de facto storage standard that competitors couldn't easily duplicate, limiting the portability of applications built to take advantage of its features without attracting undue attention from trust-busters, such as they are these days - but perhaps I'm just too cynical). - bill This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
