Subject: Re: VPS mailing list, BSD interest?
To: Darren Reed <>
From: Terry Lambert <>
List: tech-kern
Date: 10/02/1996 14:54:20
> Hmmm, having used LVM, seen ccd docs, to me, it should be something
> like this:
> +----------------------------------+
> +------------------+---------+-----+
> |                  |  LVM    |     |
> |       disks      +---+-----+ CCD |
> |                      |           |
> |    hd* sd* xd*       +-----------+
> |                                  |
> +----------------------------------+


A FS type must be able to express a preference or deny an underlying
media type.  For instance, FFS should be permitted to prevent you
putting it on a device which has Logical Device Attributes of
LDA_MAY_GROW or LDA_MAY_SHRINK, since handling of these operations
requires that the FS register a callback to allow or veto the
operation, depending on whether or not it has handlers.

Similarly, JFS/NTFS/LFS/etc. which can handle changing agregation
sizes with an LVM facility (adding or deleting PP's from the volume)
must call back to determine allowable size change increment.  I believe
JFS requires a 4M or an 8M increment, in all cases, for instance.

This is a highly complex issue.  I would warn against a soloution
that can be represented as a two dimensional image.  8-(.

					Terry Lambert
Any opinions in this posting are my own and not those of my present
or previous employers.