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.
Jeff
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