Long response -- A couple of days ago, Paul Corsa <[EMAIL PROTECTED]> advised:
> Reformat a drive completely, use either FWB or Apple Drivers(I'd > recommend Apple), do a Clean Install of OS9.1, then import whatever > you wish to save from OS8.6. Be sure you use the same file > settings(HSF or HSF+) for both HD's or the data won't interchange. > Paul C ...which touched off some discussion about compatibility between files on HFS and HFS+ file systems. Michael M <[EMAIL PROTECTED]> quite asked: > What are the consequences of dragging files from an HFS volume to an > HFS+ volume? ...as he had done many times to no apparent ill effect. Similarly, Keith Krehbiel <[EMAIL PROTECTED]> observed: > I had not realized there was a problem interchanging data between > volumes of different format. I do it all the time. Applications that > need to put files on the boot volume will do so no matter where the > applications are located/installed. What sort of problems are you > attributing to these data interchanges? kk Paul Corsa <[EMAIL PROTECTED]> responded as follows: > A drive formatted as HSF+ can read HSF or HSF+ Data. A drive formatted > in the older HSF can not read HSF+ data, i.e. there is no backwards > compatability. Paul C The issue of HFS/HFS+ compatibility is actually a little more subtle, so I thought I would take a shot at adding to the confusion. :-) First, some background. HFS and HFS+ are "file systems". File systems can be thought of as methods or structures for storing and working with (1) data "files" and (2) information about the files. For example, a file may reside in one place on a storage device, but information about the file (for example, its size and name) might reside separately in a special "directory" somewhere else on the storage device. This is why some disk utilities can rescue files from a badly damaged drive, but they might not always be able to recover the names of the files (or, less helpfully, sometimes find the filenames, but not the actual files). Anyway, there are many different kinds of file systems, and they all handle the basic tasks of storing data differently. Now, here is where we start getting to the heart of the matter, and it is where Paul's remarks might be a little misleading: "drives" don't actually "care" about file systems; they only care about transferring patterns of information between storage media and an operating system "driver". In short, drives don't "understand" file systems, but operating systems do. So why does this matter? In general, an HFS+ file system can store all of the information that an HFS file system can store, but it does so using a different "structure", and HFS+ can also store a lot more information (for example, more files and bigger files). In addition, HFS+ can store some different kinds of information than HFS can (for example, "Unicode" internationalization information). As long as (1) your operating system knows how to work with the file systems in question and (2) you or your software programs do not take advantage of any features unique to one of the file systems, you can copy data back and forth between file systems without a care. In practice, as long as you are using MacOS 8.1-9.x, you can move files from HFS to HFS+ without any worries. On the other hand, if you are moving files in the opposite direction, from HFS+ to HFS, just remember that HFS can't work with files larger than 2 GB and that an HFS file system cannot hold more than 65,356 files (pretty rare to bump into the latter limit). If you are running MacOS 8.0 or lower, the operating system doesn't know anything about HFS+, so you should only work with HFS file systems. Things get a little more complicated with MacOS X. Again, you can move files from HFS to HFS+ without much of a concern, but OS X enables some of the key HFS+ features, such as long file names (up to 255 characters). If you move a file with a name longer than 31 characters from HFS+ to an HFS file system, the name will get truncated (kind of like the old days when you would move a file called "MyFavoriteFile" from a Mac to a Windows 3.1 computer, and it would be renamed something like "MYFAVOR~.FIL"). One final caveat: because HFS+ supports a different internationalization mechanism than HFS, you might run into some problems with file names if you move files from filesystems created with different language versions of MacOS (e.g. Japanese, US English, etc.), but this is usually no more than a minor annoyance if it happens at all. Just verify that the files copied over as expected before you erase the original file system. -j PS. Someone mentioned that an audio software program which worked with HFS file systems would break if you tried to use it with HFS+ file systems. This happens because the audio software programmers wrote their own HFS "drivers" (bypassing the operating system drivers) in order to get maximum performance. Most applications don't worry about file systems -- they let the operating system handle the reading/writing to file systems. Those apps which try to avoid the OS by writing directly to a file system must therefore explicitly support each file system with its own custom driver in order to work. -- SuperMacs is sponsored by <http://lowendmac.com/> and... 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