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Re: SEUL: Partitioning

On Mon, 30 Jun 1997, Michael Peck wrote:

> Thomas Molesworth wrote:
> > 
> > On Mon, 30 Jun 1997, Jay Bloodworth wrote:
> > 
> > > How big of a performance hit do you take going through a loopback device?
> > > I haven't looked at the code, but I assume every io syscall requires two
> > > trips through the VFS layer: one for the initial call and one to perform
> > > the operation on the underlying file system.
> > 
> > The file is fixed in size+position, so it can be treated exactly like a
> > partition on the drive - this may require some kernel changes, but they
> > should be minor. I have never personally tried loopback, so I'll give it a
> > go tonight (I saw it when kernel v2.0 came out, thought "Cool!" and forgot
> > about it). I would not have thought the extra VFS step would cause too much
> > of a performance hit, but I will try it and report the findings later. I use
> > NFS over ethernet and find it fast enough.
> Forgive my ignorance, for I ask out of ignorance, but I was wondering
> what would happen to the ext2 virtual-filesystem when the user ran
> Defrag under DOS or Win95?

If it has SHR attributes, nothing - defrag doesn't touch anything with S or
H set, AFAIK (the Norton version didn't, and Win95 defrag is based on DOS
defrag is based on speedisk, the original Norton version). Anyway, as long
as LINUX.DSK is not fragmented, the start and end points could be calculated
whenever it's mounted. A fragmentation test would be easy.

Thomas Molesworth            (thomas@bass.almac.co.uk)

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