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The content of this blog is my personal opinion only. Although I am an employee - currently of Imagination Technologies's MIPS group, in the past of other companies such as Intellectual Ventures, Intel, AMD, Motorola, and Gould - I reveal this only so that the reader may account for any possible bias I may have towards my employer's products. The statements I make here in no way represent my employer's position, nor am I authorized to speak on behalf of my employer. In fact, this posting may not even represent my personal opinion, since occasionally I play devil's advocate.

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Monday, September 06, 2010

Ulfs - my user level filesystem - Andy Glew's Wiki

Ulfs - my user level filesystem - Andy Glew's Wiki: "Ulfs - my user level filesystem"



ulfs - my User Level FileSystem.

wiki: http://wiki.andy.glew.ca/wiki/Ulfs_-_my_user_level_filesystem

blog: ...

Have wanted to code this up for a long time.
Never could, because anything I did belonged to my employer.
Want it open source, so that I can use it for my personal stuff - wikis, version control.
With my current employment agreement I can work on open source, so starting.

Today got the most trivial put, get, and delete coded & tested.
Not much, but its a start.

I want a user level filesystem, with at least two bindings
* UNIX command line
* Perl
I imagine that I will eventually want python, javascript, etc.
TBD: generate such via swig?

I want command line, because I'm a UNIX old fart. I still think of the shell as a good way to compose operations, e.g. via pipes.

I want scripting languages like Perl, because much code will be in there.
But mainly because I will implement at least first version in Perl.


Storage types:
* ordinary UNIX (or Windows) hierarchical filesystem tree
* archive formats, like tar
* possibly VC tools, like git, hg, bzr, ...
** delta storage
* possibly databases, even relational
* possibly hybrid filesystem/database

: any of the above may have flavors - e.g. will have metadata in the ordinary filesystem

Filesystem Names
* use the name specified by the user
* allocate and return a name
** sequentially
** content based hashing
*** handling collisions
* metadata queries
:: all of the above, both explicit, implicit, and content based
* versioning

Command Line Interface:

mkfs:
ulfs -mkfs test.fs -type ordinary
ulfs -mkfs test.fs.tar -type tar

my $ulfs = ULFS_Ordinary::mkfs("test.fs");
my $ulfs = ULFS_Tar::mkfs("test.tar.fs");

my $ulfs = ULFS::openfs("test.fs");



basic operations
ulfs -fs test.fs -to testdata1-in-fs < testdata1 -put
ulfs -fs test.fs -from testdata1-in-fs > testdata1.retrieved -get
ulfs -fs test.fs -from testdata1-in-fs -delete

$ulfs->put(-to=>testdata1-in-fs,-input=>testdata1);
$ulfs->get(-from=>testdata1-in-fs,-output=>testdata1);
$ulfs->delete(-from=>testdata1-in-fs;

other operations
copy
move/rename
mkdir

As is my wont, some thoughts:

;Predicates
If I try to use this as a net or web based filesystem, I may want to have predicates specified by the client
executed by the server. E.g. compare-and-swap: put this file, but only if the old version's content is ...

Operations like rmdir are really simple predicates: only remove the name if that name is a directory.

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