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SubjectRe: Overmounting a filesystem
On Wed, 10 Apr 1996, Jeff Voskamp [MFCF] wrote:

> If it's not in the root directory of the partition, put it on the same
> partition as the parent directory. If it's at the root partition, put
> it on the top partition. I was going to suggest the partition with the
> most free space, but that needs too much smarts in the file system for
> my taste. You may occasionally have to mount the overlays in different
> locations to manually rebalance the loads.
>
> Hmmm.. how would mount handle this?

How about this for an off the cuff idea (well...I'm wearing a tee-shirt,
but still....)

n devices(mountable) /dev/1, /dev/2 ... /dev/n
mounted on /mnt
in this order:

mount /dev/1 /mnt
mount /dev/2 /mnt
....
mount /dev/n /mnt

Flags (sysadmin set):

Reads:
Getting the directory information in this order:
Get direntry for this dir (if it exists) for /dev/1
"" "" 2
.........
"" "" n
Cases to handle:
If /dev/k has a direntry that matches an
older direntry(/dev/1.../dev/k-1) then the older one is
thrown out (therefore inaccessable).

Writes:
Check if file exists, working /dev/n.../dev/1 Take
FIRST occurance of a matching dirent.

If file doesn't exist, write to /dev/1

Cases to handle:
/dev/k is RO: Try /dev/k+1 till /dev/n then report FS is RO.

/dev/k doesn't have enought space to write the WHOLE file.
Write what is possible, continue on /dev/k+1, etc.
untill you reach the end, then give outofspace error.

When file is closed, move all parts to one /dev/q,
searching from /dev/1..../dev/n

If not enough space is available, then report an error.


I don't like this scheme, but it's just an idea...a start, I guess.

I don't like how writes are handled. Any ideas? (I'm just
playing around.)


Christian G. Holtje (aka Doctor What)

---
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+ - + - + + + - + - + - CS major at Illinois
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also: http://www.itke.net/~docwhat

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