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SubjectRe: [PATCH] fs: Introducing Lanyard Filesystem
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On Sun, 2012-08-19 at 12:14 +0200, Marco Stornelli wrote:
> You say that you wrote a new fs because of some lacks in the other fs
> ("...I kind of invented a very simple filesystem that solves the issues
> I had with other filesystems...."). I read the website (very quickly
> actually) but I didn't find the point:
I had to be a little bit stingy with that, I haven't submitted my thesis
document yet, and I don't want to publish it before that. I may not be
allowed to do so before it is officially submission, IANAL.
At the moment, the website lacks of the information you were looking
for, sorry for that. The thesis contains also a lot of statistical data
and fancy diagrams and stuff like that. I analyzed about 600k file
stored on various removable storage devices. 80 volunteers sent in data
about their devices, generated by a program (windows) and scripts
(linux, bsd, osx) I wrote for that purpose. The data shows that people
use more complex filesystems as soon as they are confronted with
problems (mostly the 4GB limit). After that they have problems getting
their data accessed by other systems. I derived from that, that we need
a filesystem that is so simple that even unpopular operating systems can
implement it without having their business plan explode. The data will
be made public (like open data) after submitting the document. Others
are then free to derive statements from it, may then verify or
contradict my conclusions.

> what are pros and cons of this fs
> compared with existing fs?
Pros:
- Simplicity. LanyFS avoids any unnecessary complexity.
Example: I had a lot of problems reading and writing data on the Arduino
platform. Most of it was, because the platform wasn't capable of dealing
with FAT32 when files grew. I don't know if LanyFS performs better on
Arduino, I haven't written a driver for Arduino yet, I am glad I managed
to get it working on Linux for the moment.

- Interoperability. LanyFS was designed to unite those features which
are common on most operating systems. [...] All information, including
file and directory metadata, is stored in the most purposive format
without honoring the habits of any particular operating system.
Example: I have a nice FullHD movie file which is about 8GB in size. I
wanted to play that video file on a RaspberryPI connected to a TV. FAT32
wasn't able to store the file because it was larger than 4GB. I then
tried using ext3, but the ownership information from my workstation
(were the file was copied from) did not match the ones the RaspberryPI
had, since I usually do not synchronize user profiles between
workstations and embedded devices. There are workarounds, one might say,
but shouldn't it be much more easier to transfer files from one device
to another? There are use cases were modes/permissions and ownership of
files does not matter, where quota and accounting isn't necessary, where
access times don't need to be stored since they would never get updated
anyway.

Flexibility. LanyFS adopts to the underlying storage device by
adjusting its parameters accordingly. It can address block
devices starting from 4 KiB up to 64 ZiB with minimal overhead by
parameterizing the filesystem at formatting time.
Example: At the university we sometimes work with smart cards and their
sometimes "strange" filesystems. I am not an expert on smart cards and
stuff like that, but I was being told that a more simple filesystem
would be welcome. AFAIK we are talking about "disks" with a size of less
than 1MB. I don't think this is a big feature, most other fs can be
adjusted to perfectly fit a particular purpose, too. Yet there still is
the demand for something "much more simpler".

Cons:
- LanyFS is featureless. It lacks of features. This is considered a
feature by some people, and a big con by others :)

- Use of recursion. It may not scale in some cases (e.g. very large
files on embedded platforms).

- Current restrictions due to early stage. Max blocksize is 4k, but 4MB
might be better. The LWN article pointed to by Alan talks about this.

- No use of MTD/UBI features. LanyFS expects a block layer abstraction
beneath it, this is because it targets highly mobile devices, and those
devices also happen to be rotating disk (external hard drives)
sometimes. It is not optimized for flash-only devices, although most of
the devices it may run on one day will probably be flash-based.


> What problems does it solve?
- I can now watch >4GB movie files from USB thumb drive :)

- Providing a storage device interface will be easier for vendors. TVs,
car entertainment systems, digital cameras, sensor devices, navigation
systems and all kind of other devices often use FAT32 since it just
works on everyones computer, but it is limit in size. Other fs are there
to hop in, but vendors often refuse to implement them since they have to
be compatible with a lot of features. They won't face such problems with
LanyFS, it just has no features. Of course, I am just a student, I have
no money and no market power, so LanyFS might never make it into other
major operating systems or all the devices around us.

- Look around, there are so many devices that do not provide a storage
interface at the moment, but they easily could. I'd rather see my
electricity meter log my power consumption to a thumb drive than sending
it into the cloud every 5 minutes.


This whole thing isn't about the patch anymore, is it? Should we go off
list to not make so much noise disturbing other developers?
Thank you very much for your interest in LanyFS and please don't
hesitate to point out errors in the code, too.

Thanks
Dan


--
Dan Luedtke
http://www.danrl.de



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