Subject: Re: [vserver] HASH FS
From: "Michael S. Zick" <mszick@morethan.org>
Date: Fri, 25 Jul 2008 06:56:56 -0500

On Fri July 25 2008 00:50, Jun OKAJIMA wrote:
> I am not sure I answered all the questions,
> anyway, I updated the web site.
> http://www.digitalinfra.co.jp/20080720/hashfs.20080723.html
> 

Looking through that link, perhaps I can help with some talk;

The filesystem is indexed by a content identification of the target (blob).

At the index level, it is a flat file system (at least the index is).

Using a secure hash function to generate the index from the
content ensures there is only a single copy of the content present.

One example appeared in the Advanced Bash Scripting Guide (by myself)
prior to the development of GIT for indexing file changes.

Another example, using the contents of the ASUS EeePC source release
as the blobs, can be found here: 
http://sourceforge.net/project/showfiles.php?group_id=211455
Those are just the content identification base indexes; in both
single text line records or as OpenOffice Spreadsheet files.
(again, by myself).

Access to the target by name (a named file system) is secondary;
the content ID _is the name_ to interface with people and programs
using a pathname/filename structure is an indirect operation - it
actually translates pathname/filename to current content ID index.

Changes to the target (blob) content; which of course changes the
content ID, causes the pathname/filename access to index a list of
content IDs; the current one at the head, prior versions (file revisions)
following in the list.

I have never implemented a complete file system from the above, 
but Jun OKAJIMA is making an attempt at it.

The posted sourceforge files shows, as single line records, the
relationship between any content id and the path/file name of the blob.

Mike
> Probably, the page does not tell all of
> your questions, so ask me freely if
> you have any problem.
>
 
> Especially, I dont know much of vserver like you,
> so, using vserver with HASH FS is
> what I need your opinions.
> 
> And, in the long run,
> you would be able to enter VE like this.
> # vserver enter http://vserver.debian.org/etch
> Your opinion is?
> 
>             --- Okajima, Jun. Tokyo, Japan.
>            http://www.machboot.com/
>            http://www.digitalinfra.co.jp/
> 
> 
> 
> 
> 2008/7/25 John Alberts <john.m.alberts@gmail.com>:
> > Hi.  Thanks for the updated documentation.  I've read through the doc
> > and I'm still pretty confused on how to use it in relation to vserver.
> >
> > For instance,
> >
> > In the documentation, you have the following:
> > Make an index and blobs.
> > # mount -o loop,ro -t iso9660 sample.iso /mnt
> > $ cp -a /mnt aaa
> > # chown okajima:okajima /blob
> > $ find aaa | ./hashify.pl
> >
> > This whole section is confusing to me.  What are we doing here and why?
> > What is the sample.iso in this case and why am I mounting it to /mnt?
> > As this applies to vservers, vservers are usually stored under
> > /vservers.  Would we want the entire /vservers be one hashfs
> > partition, or does each guest vserver under /vserver need to be a
> > seperate hashfs partition?
> >
> > Regards,
> > John
> >
> >
> > with cp -a /mnt/aaa command, what directory are we supposed to be in?
> > What user are we supposed to use for the chown command since obviously
> > my machine doesn't have a okajima account on it?  Can it just be any
> > regular user or should it be root?
> >
> > find aaa | ./hashify.pl command, I guess here we are passing each file
> > that we just copied to the directory called aaa to the hashify.pl
> > script?
> >
> >
> >
> >
> > On Wed, Jul 23, 2008 at 10:31 PM, Jun OKAJIMA
> > <okajima@digitalinfra.co.jp> wrote:
> >> 2008/7/22 Jun OKAJIMA <okajima@digitalinfra.co.jp>:
> >>> For ML issue, the answer is "not for now".
> >>> Of course, I know I have to make it before very long.
> >>>
> >>> If you have to contact me just now,
> >>> using vserver ML or OpenVZ ML.
> >>> I subscribe them all.
> >>>
> >>> For implementation docs, I am writing now.
> >>> just wait a bit.
> >>>
> >>
> >> Done. See this.
> >> http://www.digitalinfra.co.jp/20080720/hashfs.20080721.html
> >>
> >>            --- Okajima, Jun. Tokyo, Japan.
> >>           http://www.machboot.com/
> >>           http://www.digitalinfra.co.jp/
> >>
> >>
> >>>
> >>
> >
> >
> >
> > --
> > John Alberts
> >
> 
>