Re: Toronto Filsystem?
Trever Adams (arabian@onramp.net)
Sun, 01 Mar 1998 01:18:26 -0600
> From: "Benjamin C.R. LaHaise"
> Date: Sat, 28 Feb 1998 19:14:09 -0500 (EST)
> Subject: Re: Toronto Filsystem?
>
> On Sat, 28 Feb 1998, Albert D. Cahalan wrote:
> ....
> > I think this could get ugly when someone appends to a 1000 MB file.
> > You might want an inode hack that indicates "blocks in this file
> > before #345987 are specified by inode 42 on the layer below".
>
> Actually, this is easier than it seems. A simple restriction that makes
> everything work well is to require that all underlying layers be made
> read-only, which avoids a mess of consistency problems. Then, use a top
> layer that supports sparse files. Reading a file becomes: try layer one -
> oh, not there; try layer 2... No, I don't have working code yet.
>
> -ben
>
Not cool at all. Once the original file owner updates the file (say the
group agrees on a new standard, or root updates the file) any way but
clean implimentation and write of the entire modified file becomes
corrupted. You cannot ignore the possibility of under layers being
modified, especially if you want multiple layers (beyond 2). This is
true with spares files or the way the way suggested by the post you
responded to. Once an upper layer diverges (by modification not by
"WHITE OUT") it must forever remain independent for that file. I see no
way around it.
As always, if I am wrong, please correct.
~~~~~~~~~~~~~~~~~~~
Trever Adams
arabian@onramp.net
http://rampages.onramp.net/~arabian/silent.htm
~~~~~~~~~~~~~~~~~~~
"No man knows how bad he is till he has tried very hard to be good."
~C.S. Lewis
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