future disk storage enhancements

[David A. Higgen]

I'm going to be working shortly on ways of extending disk storage over more
than one physical disk ("logical volumes", "multi-spindle filesystems" 
or what-have-you).

I'd be glad to have ideas/comments/wishlists from interested parties. 

Some initial questions.

1) Is your interest in this mainly:
 
   a) A need for larger storage, ie more files in a filesystem, or

   b) A need for really long files?

   If the latter, what sort of file sizes do you think might arise in practical
   applications for our systems over the next year or so?

2) Is there any percieved need for large RAW (ie non-filesystem) storage?

3) To address large storage objects, we would have to augment the semantics
   of 'lseek' in some way. Two possibilities: 
   
      *	extra defines in the "whence" field specifying units of (say) Kbytes
	instead of bytes.

      * A new system call taking more than one word to allow a larger
	range. (Presumably 64 bits, probably typedef'd for convenience).

   Preferences? Alternatives?

   Is there really a need to address very large storage objects to byte
   granularity?

4) How important is extensibility? (ie the ability to add the space of a new 
   disk to an existing filesystem). If this IS considered important,
   must it be totally dynamic (ie can be done even when the filesystem is
   mounted and in use) or could we live with needing to unmount the
   filesystem to extend it?

5) Do you foresee any demand for 'mirroring' ie automatically keeping data
   on duplicate/triplicate etc storage for reliability? (We are not currently
   in the database/transaction-processing market where this is common, but
   who knows)....