Subject: Re: as long as we're hitting FFS...
To: Perry E. Metzger <>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 03/23/1999 18:46:28
On Tue, Mar 23, 1999 at 06:19:58PM -0500, Perry E. Metzger wrote:
> As long as we're going to hit the inode format, and creating a new
> magic number, some things I'd like fixed from the wish list:
> 1) Eliminate the remaining file size limits. As it stands, you can't
> actually have an FFS file of 2^63rd size, although the system calls
> are all fine.
> 2) Expand time in inodes to 64 bits of seconds. Sure, we have 39 years 
> to do it but I see no reason not to do it now given the relative
> expense of writing an inode to disk vs. the expense of the extra
> couple of operations.
> 3) Eliminate endianness of FFSes -- this is more controversial. Right
> now, we have bi-endian support, but it would be cool not to need it.
> 4) GC old goo like the old uid/gid support.

Speaking of "old goo" -- I'd like to propose rotational position optimization
as "old goo" that is not useful on any disks manufactured in almost 10 years,
costs CPU, and needlessly complicates the data structures.

In fact, if we're changing the filesystem enough to require a magic number
change, I'd think *all* the stuff that tries to understand the disk layout
(aside from "close by block number") could go.  It just can't describe
modern disks, for which you often can't get the real data anyway.

Also, it'd be nice to support more fragmentation than the current 1/8
limit, so we could use larger blocks without wasting so much space
(and avoid the need to cluster in many cases -- though the current
limitation of only being able to cluster to MAXPHYS, which is a lot smaller
than the actual maximum size transfer you could get across the buses to the
disk on many buses/controllers/disks on many ports, is kinda a separate
though related lose, and this wouldn't help avoid it).

Basically, if we're going to introduce a "new FFS", maybe it'd be better
to do so for more than one fairly small (if useful and cool) change.  I
don't think we should bump the magic number for just this, not in a
public release at least.

Thor Lancelot Simon	                            
	"And where do all these highways go, now that we are free?"