You don't have a cache of the Shadows papers, by any chance? The URLs referenced appear outdated.
Cheers, Christian On Mon, 5 Apr 2004, Doug Currie wrote: >Monday, April 5, 2004, 6:13:18 AM, Christian Smith wrote: > >> On Wed, 31 Mar 2004, Joel Lucsy wrote: > >>>Just for the record, for Windows machines, only NTFS v5 formatted >>>drives/partitions support sparse files. Windows 2000 or better are the >>>only ones supporting NTFS v5. This means Win9x and FAT32 drives under >>>2000/XP won't be able to use sparse files. > >> There are bigger problems anyway. > >> A snapshot of all old data would be required to be maintained for all >> active readers, even if a write transaction has finished. [...] >> SQLite would need to maintain a snapshot for each reader, with nothing >> but the filesystem to use for IPC. A difficult problem. > >This is *precisely* the problem my Shadow Pager solves. >http://www.sqlite.org/cvstrac/wiki?p=BlueSky > >> A snapshot might be feasible to maintain from within the same >> process, but that would limit concurrent readers and writer to the >> same process. [...] > >Indeed my Shadow Pager design is limited to one process, but I believe >that it can be extended to multiple processes by maintaining a list of >active transactions, each with a list or bitmap of freed pages, in a >lockable shared file. > >> This gives us the benefit of the better performance the undo based journal >> gives us, rather than the redo based journal would give us (redo requires >> at least 1 read and 2 writes per page, undo requires 1 read and 1 write >> per page in commit.) > >Shadow Pager requires 1 write per commit, regardless of the number of >pages written. There are of course other overheads during the >transaction, comparable to the above in cost. > >e > >>>Christian Smith wrote: >>> >>>>How about taking advantage of sparse files (most OS support sparse files) >>>>for the journal, and saving the redo pages in the new shadow file. Thus >>>>the burden of efficiently handling mapping is bumped down to the OS. >>>> >>> > -- /"\ \ / ASCII RIBBON CAMPAIGN - AGAINST HTML MAIL X - AGAINST MS ATTACHMENTS / \ --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
