Re: Request: Test suite for EFS.



bob@thestuff.net wrote:
> 
> On Thu, 17 Feb 2000, Kent Schumacher wrote:
> 
> > bob@thestuff.net wrote:
> >
> > > First, a few questions. What file system does EFS use? Is it something
> > >that any unix that supports mounting a file vea loop back can mount? Is it
> > > a standard file system? If not, being able to read the file by any non
> > > gnome app would be difficult to implement. Also, why EFS? Can gnome-vfs
> > > not do what you want? No one commented on the use of tar as the file
> > > system to maintain portability. What do you guys think of it?
> > >
> >
> > Regarding tar files.
> >
> > Tar has at least 3 shortcomings.
> >
> > 1) There isn't an index to allow quickly moving to a given data item.
> 
> Well, when the file is first opened, that info could be cached to allow
> faster access.
> 
> > 2) There isn't any way to insert a data-element that has grown without
> >     re-writing the whole file
> > 3) There isn't any way to remove or shrink a data-element without rewriting
> >     the whole file.
> >
> > It's interesting to note that points 2 and 3 are problems that are common to any sort of
> > storage management system, be it malloc, a filesystem, or a data-base.
> 
> Well, if a file system already has the same problem, just use its solution
> on the tar fs problem. Im sure that the tar libs that already exist have
> the limitations that you have stated, but I dont see why a new lib that
> doesnt have the limitations couldnt be created.
> 
Tar and XML have these problems because they are linear formats.
And even if you cache the data in memory, at some point you would have to write
out the whole file.

Filesystems and databases are not linear, they use blocks of storage space
and then recombine, in memory, the blocks into files/tables/streams through
various machination.

For filesystems and databases problems 2 and 3 do not cause full rewrites, 
only directory structures and the blocks of files affected have to be rewritten.

Your harddisk is not rewritten every time you edit a file, only the changed
block are.



The complaint about using a block system (which i assume EFS is) is that it is
not the "Right Thing" to do because the format is 
not linear and fully text (and therefore harder to
manage/decode) and there is no one block
format with the force of the "industry" behind it. 

--
Krzysztof Kamieniecki
QC Solutions, Inc.
phone:1.978.313.0300 x114
mailto:krys@qcsolutions.com



[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]