[Gluster-devel] AFR over somewhat slower link

[Paul Arch]

Hi,

 Sorry if this has been answered before, I did take a quick delve but
couldn't find explicitly an answer.

 We are looking at setting up AFR over initially a 10Mb point to point link
with ping times ~ 70ms return.  This will progress up to 100Mb as required.

** Hope this comes out ok apologizes if it doesn't **
        
[ Internet ]  --->    [    CPU    ]   ->        ( glusterfs client )
                                                ( glusterfsd  primary
storage)
                                                |               
                                                                |  { 10Mbit
point to point  / AFR translator}
                                                                |
                                                        ( glusterfsd
secondary storage)

My questions are ;

1.  When the process on CPU WRITES to the glusterfs, does it wait until the
write is confirmed @ secondary storage before return ?
( will we see our software systems block until this happens, or does the
write hit the glusterfs client, it returns OK and the software continues )

2.  When the process on CPU READS, will it only attempt to read from the
primary storage, UNLESS for some reason it is un-available ( in which case
it would switch to secondary storage )
( or will it try to combine read from both PRIMARY and STORAGE to serve the
requirements for glusterfs -> CPU ? )

3.  Assuming AFR is working correctly between the primary and secondary
storage, is it possible to setup a 'read/only' translator off the secondary
storage ? :

                           ..........................
                                        |  { 10Mbit point to point  / AFR
translator}
                                        |
                                ( glusterfsd secondary storage)
            [ CPU ] <---( glusterfs client )

         Bearing in mind that the glusterfsd primary and secondary will be
both utilising unify translator also ( otherwise we could just mount the FS
)

4. Sorry this one is probably quite obvious but I couldn't find an answer to
it ( or is it too obvious !! )  Is this topology OK ?

        [CPU]                   [CPU]                    [CPU]
        ( glusterfs )   ( glusterfs )   ( glusterfs)
                |                       |                       |
                ----------------------------------------
                ( glusterfsd  primary storage)

So several CPU/Glusterfs clients hit one glusterfsd direct, rather than
having to stuff say a NFS client in front of the glusterfs to serve the
clients



-- 

Paul Arch 

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