[Gluster-devel] Fwd: Gerry Reno .vol files and scripts

[Gerry Reno]

Krishna Srinivas wrote:
> Hi All,
>
> Maybe this piece of information will benifit others too, in case you
> are confused about using -n option during glusterfs mount.
>
> ---------- Forwarded message ----------
> From: Krishna Srinivas <krishna at zresearch.com>
> Date: Jul 3, 2007 9:30 PM
> Subject: Re: Gerry Reno .vol files and scripts
> To: Gerry Reno <greno at verizon.net>
>
> Gerry you are not getting it ....
>
> See, -n option should not be used in normal cases, its used normally
> during debugging, say when you want to override the topmost translator.
>
> If you really want to use -n option, just give -n afr which is the 
> name of
> the afr volume in your spec. which is same as not using -n option.
>
> Internally, when glusterfs process is started, it arranges the
> xaltors like this:
>
>                   ------>client0
> fuse --->afr ---->client1
>                   ----->client2
>                   ------>client3
>
> i.e fuse talks to afr, and afr talks to client0, client1, client2, 
> client3
>
> However if you give "-n client0", the arrangement will be like this:
>
> fuse--------------->client0
>               afr ---->client1
>                   ----->client2
>                   ------>client3
>
> So fuse will directly talk to client0, so afr does not even come into
> picture, so no files are replicated.
>
> I dont know if the diagrams will reach you in a proper formatted way.
>
> Come to IRC if it does not make sense.
>
> Krishna
>
>
>
>
> On 7/3/07, Gerry Reno < greno at verizon.net> wrote:
>> >> > Krishna Srinivas wrote:
>> >> >>>>>>>> Yes '-L DEBUG' is declared.
>> >> >>>>>>>> glusterfs -l /var/log/glusterfs.log -L DEBUG --spec-file
>> >> >>>>>>>> /usr/local/etc/glusterfs/test-client.vol -n client0
>> >> >>>>>>>> /mnt/glusterfs0/
>> >> >>>>>>>>
>> >> >>>>>>>>
>> >> >>>>>>>>
>> >> >>>>> you should not give -n client0 here, it will override the afr
>> >> >>>>> translator.
>> >> >>>>> Hence you are not seeing any replication!
>> >> >>>>>
>> >> >>>>>
Krishna,
  For the sake of completeness I'm also going to post my response to the 
above:

Krishna,
 Now that you show this it makes some sense.  But to just see options to 
glusterfs which says use '-n' to select which volume, well that does not 
say anything to me about the fact that this breaks AFR.  You are so 
close to the code that for you this is obvious but for those not close 
to the code this is not obvious.  And if there is some type of 
incompatibility between '-n' and AFR then this needs to be documented 
and also warning messages need to be present during it's use.

Gerry