Re: [tlug] distributed file systems

[Curt Sampson <cjs@example.com>]

On 2010-02-15 11:21 +0900 (Mon), Sach Jobb wrote:

> We are setting up some local servers in the UK and and the US and I
> am thinking about implementing a distributed file system in order
> to solve data syncing problems. I first came across this looking at
> mogilefs....

While mogilefs can be considered a "file system," it's not a file system
like one you'd put on a hard disk or an SD card. First, it's accessed
through protocols such as HTTP, which makes it a "file system" in the
same sense as your friend's blog is a file system. Second, and more
subtly, it doesn't have what we call "POSIX semantics," which means that
certain operations behave quite differently from the ext4fs or whatever
you happen to use as the root filesystem on the Linux box sitting in
front of you. This has deep implications, but the main one is that, even
if you did put some software in between you and it to let you access it
as if it were just another drive mounted on your system, the behaviour
will be subtly different, and this make break both programs and your
security expectations.

> ...I have recently found a couple of fuse-based solutions: xtreemfs
> and hdfs. Does anyone have any opinions/recommendations/experiences on
> these (or others)?

My very strong recommendation is that you, for the moment at any
rate, drop the idea of using a distributed file system, and instead
of describing a proposed (and probably poor) solution to an unknown
problem, instead describe the problem itself. It's almost certain that
a "distributed file system" in the sense of something like NFS either
won't work well for you or be rather insecure or both.

So what do you need to share, and how and with whom do you need to share
it? Give us the whole process. What format is the data? Who's creating
it? Who's reading it? Who's updating it?

By the way, I'd lay greater than 50% odds that you'd be best served by a
version control system. I don't know if you saw Steve's talk on this at
the January TLUG, but if not this would be an area worth spending some
time researching, even if it's not the solution you'll eventually use,
because it does address a lot of common problems in file sharing.

cjs
-- 
Curt Sampson         <cjs@example.com>         +81 90 7737 2974
             http://www.starling-software.com
The power of accurate observation is commonly called cynicism
by those who have not got it.    --George Bernard Shaw