Re: Distributed storage. Move away from char device ioctls.

J. Bruce Fields
2007-09-14T21:12:30Z

On Fri, Sep 14, 2007 at 03:07:46PM -0400, Jeff Garzik wrote:
> My thoughts. But first a disclaimer: Perhaps you will recall me as one
> of the people who really reads all your patches, and examines your code and
> proposals closely. So, with that in mind...
>
> I question the value of distributed block services (DBS), whether its your
> version or the others out there. DBS are not very useful, because it still
> relies on a useful filesystem sitting on top of the DBS. It devolves into
> one of two cases: (1) multi-path much like today's SCSI, with distributed
> filesystem arbitrarion to ensure coherency, or (2) the filesystem running
> on top of the DBS is on a single host, and thus, a single point of failure
> (SPOF).
>
> It is quite logical to extend the concepts of RAID across the network, but
> ultimately you are still bound by the inflexibility and simplicity of the
> block device.
>
> In contrast, a distributed filesystem offers far more scalability,
> eliminates single points of failure, and offers more room for optimization
> and redundancy across the cluster.
>
> A distributed filesystem is also much more complex, which is why
> distributed block devices are so appealing :)
>
> With a redundant, distributed filesystem, you simply do not need any
> complexity at all at the block device level. You don't even need RAID.
>
> It is my hope that you will put your skills towards a distributed
> filesystem :) Of the current solutions, GFS (currently in kernel) scales
> poorly, and NFS v4.1 is amazingly bloated and overly complex.
>
> I've been waiting for years for a smart person to come along and write a
> POSIX-only distributed filesystem.

What exactly do you mean by "POSIX-only"?

--b.