[Gluster-users] novice kind of question.. replication(raid)

[RW]

> many thanks Robert for your quick reply,
> I still probably am missing/misunderstanding the big picture here, what
> about this:
> 
>                             box a  < -- >  box b
>                             /dir_1             /dir_1
>                               ^                     ^
>         serivces locally                     services locally
>    read/write to dir_1                     read/write to /dir_1

This is basically the setup I described with my config files.
/dir_1 (or /some_folder in you former mail) is the client mount.
Everything you copy in there will be replicated to box a and
box b. It doesn't matter if you do the copy in box a or b.
But you need a different location for glusterfsd (the GlusterFS
daemon) to store the files locally. This could be /opt/glusterfsbackend
for example. You need this on both hosts and you need the mounts
(client) on both hosts.

> - can all these local services/processes, whatever these might be,
> not know about mountig and all this stuff?

You need to copy glusterfsd.vol on both hosts e.g. /etc/glusterfs/
Then you start glusterfsd (on Gentoo this is "/etc/init.d/glusterfsd
start"). Now you should see a glusterfsd process on both hosts.
You also copy glusterfs.vol to both hosts. As you can see in my
/etc/fstab I supply the glusterfs.vol file as the filesystem
and glusterfs as type. You now mount GlusterFS as you would do
with every other filesystem. If you now copy a file to /some_folder
on "box a" it will automatically be replicated to "box b" and after
that it will be immediately be available at "box b". The replication
is done by the client (the mountpoint in your case if this
helps to better understand). The servers basically only provide the
backend services to store the data somewhere on a brick (host).
In my example above this was /opt/glusterfsbackend.

> - and server between themselves make sure(resolve conflicts, etc.)
> that content of dir_1 on both boxes is the same?

Most of the time ;-) There're situations where conflicts can
occur but in this basic setup they're seldom. You have to monitor
the log files. But GlusterFS provides self healing which means
that if a backend (host) goes down the files generated on the
good host - while the bad host is down - will be copied to the failed
host if it is up again. But this will not happen immediately.
This is the "magic part" of GlusterFS ;-)

> - so whatever happens(locally) on box_a is replicated(through "servers")
> on box_b and vice versa,
> possible with GlusterFS or I need to be looking for something else?

As long as you copy the files into the glusterfs mount (in your
case /some_folder) the files will be copied to "box b" if you
copy it on "box a" and vice versa.

> and your configs, do both files glusterfsd and glusterfs go to both
> box_a & box_b?

Yes.

> does mount need to be executed on both boxes as well?

Yes.

- Robert


> thanks again Robert
> 
> 
> 
> On 16/04/10 13:42, RW wrote:
>> This is basically the config I'm using for replicate
>> a directory between two hosts (RAID 1 if you like ;-) )
>> You need server and client even both are on the same
>> host:
>>
>> ##########################
>> # glusterfsd.vol (server):
>> ##########################
>> volume posix
>>   type storage/posix
>>   option directory /some_folder
>> end-volume
>>
>> volume locks
>>   type features/locks
>>   subvolumes posix
>> end-volume
>>
>> volume server
>>   type protocol/server
>>   option transport-type tcp
>>   option transport.socket.bind-address .......
>>   option transport.socket.listen-port 6996
>>   option auth.addr.locks.allow *
>>   subvolumes locks
>> end-volume
>>
>> #########################
>> # glusterfs.vol (client):
>> #########################
>> volume remote1
>>   type protocol/client
>>   option transport-type tcp
>>   option remote-host <ip_or_name_of_box_a>
>>   option remote-port 6996
>>   option remote-subvolume locks
>> end-volume
>>
>> volume remote2
>>   type protocol/client
>>   option transport-type tcp
>>   option remote-host <ip_or_name_of_box_b>
>>   option remote-port 6996
>>   option remote-subvolume locks
>> end-volume
>>
>> volume replicate
>>   type cluster/replicate
>>   # optionally but useful if most is reading
>>   # !!!different values for box a and box b!!!
>>   # option read-subvolume remote1
>>   # option read-subvolume remote2
>>   subvolumes remote1 remote2
>> end-volume
>>
>> #####################
>> # /etc/fstab
>> #####################
>> /etc/glusterfs/glusterfs.vol /some_folder  glusterfs  noatime  0  0
>>
>> "noatime" is optional of course. Depends on your needs.
>>
>> - Robert
>>
>>
>> On 04/16/10 14:18, pawel eljasz wrote:
>>   
>>> dear all, I just subscribed and started reading docs,
>>> but still not sure if I got the hung of it all
>>> is GlusterFS for something simple like:
>>>
>>> a box <->        b box
>>> /some_folder                      /some_folder
>>>
>>> so /some_folder on both boxes would contain same data
>>>
>>> if yes, then does setting only the servers suffice? or client side is
>>> needed too?
>>> can someone share a simplistic config that would work for above simple
>>> design?
>>>
>>> cheers
>>>
>>>
>>>
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