On Fri, May 2, 2008 at 8:40 AM, Brandon Lamb <brandonlamb@xxxxxxxxx> wrote: > > On Fri, May 2, 2008 at 3:04 AM, Daniel Maher <dma+gluster@xxxxxxxxx> wrote: > > > > On Thu, 1 May 2008 14:47:39 -0700 "Brandon Lamb" > > <brandonlamb@xxxxxxxxx> wrote: > > > > > http://www.gluster.org/docs/index.php/Setting_up_AFR_on_two_servers_with_client_side_replication > > > > > > Look over and make sure it is kosher? > > > > > > I added a section at the bottom for "gotchas", can you take a quick > > > look to make sure they are accurate statements. > > > > From the wiki page : > > > > "As you can see the cluster came back. During the time that server2 is > > down, the file system does not seem to be available. This does not bode > > well when we need or want to be able to down one of the data servers > > for whatever reason. Hence client side AFR is recommended over server > > side." > > > > IMHO, the conclusion that you've drawn here is somewhat misleading. By > > using RRDNS to allocate a single hostname to all (both) nodes in the > > AFR server cluster, the problem you're describing can be avoided > > entirely. > > > > While i realise that your wiki articles are meant to be as simple as > > possible (and, therefore, a discussion of RRDNS is out of scope), it > > would be remiss to not (at least) link to further information on the > > subject. > > > > > > -- > > Daniel Maher <dma AT witbe.net> > > Actually from what I am seeing in my testing that would not be true. > Also with RRDNS you would have dns ttl issues where you could be > directed to a server that was down? I use LVS for all my major > services so dont run into that problem. > > However, that aside, rrdns would not solve this problem. client1 was > still connected to server1 which was up and running, but it could not > read or write to existing files, although i was able to create a NEW > file for some reason while server2 was down. So using rrdns to make > the clients connect to a working server *so far from what I am seeing* > would not solve anything. Yes it would get a client to connect to > server1 which was up, but the cluster still doesnt work. > > I will be more doing more extensive testing today per request by > Krishna with debugging on and updating wiki as needed. More to come! > Hopefully I just have something goofy going on. > > NOTE TO KRISHNA: > Could this have ANYTHING to do with the possiblity that I am using two > network interfaces? Could it for *some* reason be getting confused > that server1 and server2 are talking on 192.168.0 and my clients are > talking to the servers on 208.200.248? > > I will test this out as well A note on RRDNS, maybe my understanding is incorrect, can anyone comment? My understanding is that if you have two A records say 192.168.0.1 and 192.168.0.2 for a name "servers.mycluster.tld" that client1 will do a dns lookup for servers.mycluster.tld and get an answer of ;; ANSWER SECTION: servers.mycluster.tld. 3600 IN A 192.168.0.1 servers.mycluster.tld. 3600 IN A 192.168.0.2 and it may get those in any/either order. Will it actually TRY both or will it just use the first of the two answers it gets back? I realize that mail server software is suppose to try the lowest MX priority entry for a domain first and then the next highest as a server is unavailable, but isnt this a function of the server software? Does glusterfs do this as well? >From what I knew, rrdns could be a "poor man's" solution for LVS as a way to try to distrubute load, but if a server was down clients would still be directed to them (and fail). Corrections?
