On 19 Sep 2016, at 2:52am, Keith Medcalf <kmedc...@dessus.com> wrote:

> That is to say there is no difference between a block device (such as a 
> physical hard disk) attached to the computer via a 1 foot SCSI cable and an 
> iSCSI LUN where the iSCSI block device is located on a different plant, other 
> than the latency of the command/response.  In both cases you are using a 
> "Local" filesystem.
> This is vastly different from mounting a "remote shared filesystem" from 
> another computer, whether that computer is located in the next rack slot or 
> located on another planet.

And it's going to get worse since the next generation is 'cloud storage' which 
looks like what you've called "remote shared filesystem" but has no fixed 
hardware.  It can be addressed using a network file system (SMB2 / CIFS / NFS) 
but the programmer will have no idea whether their data ends up on a rotating 
disk next door or spread over six SSDs on four continents.  So on top of the 
current problems it exhibits unpredictable timing problems.

We just have to pray that the network file system implements locking properly.  
Which SMB2 does allow, but I have no idea whether any drivers actually do it 

Hmm.  Earlier this year Apple announced it's working a new file system, 
designed for the modern age with some pretty neat abilities.  It's suited to 
everything from Smart Cards to snapshottable virtual partitions in the cloud.  
Apple said it will release open source drivers and make the whole thing 
unencumbered by patents.  Now if it could just do the same thing with an API 
which implements locking correctly ...

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