Messages in this thread | | | From | Eric Kasten <> | Subject | Re: A though on multi-session cds | Date | Thu, 7 Oct 1999 15:55:02 -0400 (EDT) |
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> On Thu, 7 Oct 1999, Steve Dodd wrote: > > > On Thu, Oct 07, 1999 at 09:59:54AM -0400, Eric Kasten wrote: > > > > > A thought on multi-session cds. I've been considering using CD-Writers > > > as a way to create snapshots of certain types of critical data by > > > writing a new track to the CD periodically (essentially creating a set > > > of generation datasets on the CD). One of the down sides of this > > > is that there isn't a particularily easy way (that I've located) to access > > > the data tracks beyond track 01 -- ie, mount mounts track 01, but there > > > isn't a way to mount a different track that also has an isofs on it. > > > > isofs in 2.3.x (for suitable values of x, certainly >=15) has a > > session= parameter that you should be able to pass in via mount. > > > > What would be even more interesting is for cdrom block devices to make > > multiple sessions appear as partitions -- assuming people don't ever put > > _real_ partition tables on CD-ROMs, of course. > > I once used a multisession CD-ROM (don't recall the brand) whose authoring > software and device driver allowed for incremental backups. The driver > would present the multisession CD-ROM as one filesystem where you only saw > the most recent version of a given file. It was pretty slick.
That would be a lot like having a CD-ROM filesystem that acted like an inherited filesystem. Thus, you could do a backup on track 1 and then incrementally write only the files that had changed to subsequent tracks. When you mounted the CD-ROM you'd see only the latest versions of the files that were backed up. I remember their being an IFS in the kernel sometime ago, but it disappeared (I think (?)).
...Eric
Eric Kasten kasten@nscl.msu.edu
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