Path: utzoo!attcan!uunet!mcsun!ukc!warwick!cudcv From: cudcv@warwick.ac.uk (Rob McMahon) Newsgroups: comp.unix.large Subject: Re: Epoch like filesystem Message-ID: <1990Oct16.105009.8285@warwick.ac.uk> Date: 16 Oct 90 10:50:09 GMT References: <60058@bbn.BBN.COM> Sender: news@warwick.ac.uk (Network news) Organization: Computing Services, Warwick University, UK Lines: 29 In article <60058@bbn.BBN.COM> chowe@bbn.com (Carl Howe) writes: >[In Plan 9] They back up the entire contents of their hard disk to optical >every night as part of the standard file system tree. For example, all files >created or changed today would end up in the file system under /1990/1015/... >Yesterday's files would be under /1990/1014/.... The hard disk on any given >day only contains the changes since the last optical backup. You end up with >both fast access to recently created data and on-line access to all backups. Surely you want the recently *accessed* data, not just the recently *created* data on hard disk ? Otherwise your system's going to be a bit slow. >Of course, they have a separate file server machine to do all this magic. >You'd have to modify the file system to make all the copy on write stuff work >correctly. However, perhaps you could simply make it a new file system type >and run it off the file system switch stuff... This sounds like an ideal application for SunOS 4.1's Translucent FileSystem (TFS), where you can have a stack of filesystems mounted one over the other, with the ones below showing through the holes in the ones above. Just mount your hard disk on top of your /1990/1015 system on top of your /1990/1014 system... When you alter a file it is automatically copied to the top level. I think you'd still have to have some mechanism to copy recently accessed stuff up to the top level too. Is anyone doing anything like this ? Rob -- UUCP: ...!mcsun!ukc!warwick!cudcv PHONE: +44 203 523037 JANET: cudcv@uk.ac.warwick INET: cudcv@warwick.ac.uk Rob McMahon, Computing Services, Warwick University, Coventry CV4 7AL, England