RE: (reiserfs) Re: LVM / Filesystems / High availability
Amsden, Zachary (amsdenz@aavid.com)
Thu, 25 Jun 1998 08:26:36 -0400
> On Wed, 24 Jun 1998, Amsden, Zachary wrote:
>
> >
> > > > ... and fs resizing on Linux will need fs support too. Again,
> the
> > > > question is, given that the fs needs to add support, do we need
> > > resizing
> > > > support at the block device layer TOO? Or is that just extra
> > > > unnecessary complexity? I for one would be quite happy with a
> > > scheme in
> > > > which the filesystem could span multiple block devices; that
> would
> > > allow
> > > > shrinking and growing at will, without any complex interaction
> > > > requirements between the filesystem and the block device layers.
> > >
> > > Yes. there must be some layer which maintains the available
> > > block devices (and provides the user level tools). This should be
> > > done in a file system independend manner.
> > > All file systems could be used and with LVM and specifically
> adapted
> > > file systems could even re-size online (at least enlarging a fs
> may
> > > be possible).
> > >
> > Agreed. Any useful filesystem is resizeable
> > offline and thus could benefit from LVM devices.
> > This does require the developement of special
> > tools for each FS type to do the resize. It
> > doesn't require any change to FS kernel code.
> >
> > When you start talking about dynamically
> > resizeable filesystems, then you need to change
> > the kernel FS code, because the active FS needs
> > to be aware of what changes are going to occur
> > on the block level, may need to prepare for
> > these changes and clean up when they are done.
>
> When you move an alocated PE on an LV to another PV, it is transparent
> to
> the FS using the LV... Any questions?
>
> -Shawn
>
Yes, how is it transparent when you remove an allocated
PE from a non-RAID striped logical volume? If it has
data on it, the FS needs to move the data and has to be
informed that there are now fewer free blocks. There
are ways to get around moving data in some cases, but
not in all.
Also, since I'm new to this discussion I find PE, etc.
not quite clear. I'm assuming PE=partition entry
LV=logical volume, PV=physical volume
Does anyone think this discussion would be carried out
better on the new linux-fsdevel list?
Zach
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