Gluster users - Oct 2016 - How gluster parallelize reads

> > 0 means use the first server to respond I think - at least that's
my guess
> > of what "first up server" means
> > 1 hashed by GFID,  so clients will use the same server for a given
file but
> > different files may be accessed from different nodes.
> 
> I think that 1 is better.
> Why "0" is the default ?
Basic storage-developer conservatism.  Zero was the behavior before
read-hash-mode was implemented.  As strongly as some of us might believe
that such tweaks lead to better behavior - as I did with this one in
2012[1] - we've kind of learned the hard way that existing users often
disagree with our estimations.  Thus, new behavior is often kept as a
"special" for particular known environments or use cases, and the
default is left unchanged until there's clear feedback indicating it
should be otherwise.

[1] http://review.gluster.org/#/c/2926/

2016-10-03 20:48 GMT+02:00 Jeff Darcy <jdarcy at
redhat.com>:
> Basic storage-developer conservatism.  Zero was the behavior before
> read-hash-mode was implemented.  As strongly as some of us might believe
> that such tweaks lead to better behavior - as I did with this one in
> 2012[1] - we've kind of learned the hard way that existing users often
> disagree with our estimations.  Thus, new behavior is often kept as a
> "special" for particular known environments or use cases, and the
> default is left unchanged until there's clear feedback indicating it
> should be otherwise.
That's fine, but i've not found description of these values in docs.
is it documented ?
Anyway, in gerrit you are talking about "local" reads. How could you
have a "local" read? This would be possible only mounting the volume
locally on a server. is this a supported configuration?

And, as you write, the local server ins't always the faster to
response, thus is not a good check.
Probably, a "priority" could be added in mount option, so that when
mounting the gluster volume i can set the preferred host for reads.

Something like this:

mount -t glusterfs -o preferred-read-host=1.2.3.4 server1:/test-volume
/mnt/glusterfs