On Mon, 21 Aug 2006, Ez-Aton wrote: > RH Cluster is a bad joke.
linux-ha is also not so good (e.g. it cannot recover from loss of access to external disks). > I have used various HA solutions, including VCS, SunCluster, HACMP, and > even MSCS, and without a doubt, RH Cluster sux. It lacks features, and > its main defensemechanism against split-brain is "Shoot the Other in > the Head" via its UPS, it's Fibre link, or the likes (they call if > "Fence"). Instead of better logic (how to detect split-brain? How to > prevent it?), they use brute-force in a way I didn't like. there is no theoretical solution to a real "split brains" situation. most clustering software use some sort of SCSI reservation to prevent this - but then, if the split is complete - there'll not be proper access to the disks anyway (and in a real HA system, you have two sets of disks - so there can be a split between them as well). > In my simple tests (used HTTPD as a resource) the cluster was unable to > recover from a simple "pkill httpd" on the active node, and completely > flunked my tests. > > > I would recommend you check Linux-HA. It is looking OK, seems adjustable > to your needs, and would probably work better. It is a bit more > complicated to setup (although it's not too complicated), but it can be > controlled via simple scripts, which can probably do what you wanted it > to do. albeit linux-ha being better - it is too problematic (and uses the same STONITH method during split-brains - and ofcourse STONITH can't work when there is a real communications problem between the two servers). note that there are some commercial cluster software for linux, which looks far better, features-wide, when compared to redhat cluster or to linux-HA. > Ez. > > > Ira Abramov wrote: > > > Quoting Vitaly Karasik, from the post of Sun, 20 Aug: > > > >>> so, is there a config error here, or should I dump the whole iSCSI > >>>concept? is there a way to install a red-hat cluster of three > >>>CENTOS3 machines with no common storage? I just need IP addresses > >>>and processes moving around between the nodes, the application > >>>vendor ONLY supports Red Hat 3 and its clustering, but won't supply > >>>instructions or recommended procedures. arrrrggh! > >>> > >> As far as I remember, RHEL3 Cluster Manager cannot work without shared > >> storage anddoesn't support iSCSI device as a shared storage (at > >> least, RH doesn't promise that this configuration will work stable) > >> > > > > it works just fine. RHEL Cluster with two common raw devices for the > > quorum, I didn't bother setting up GFS atthe end, since it was not > > important. > > > > I was very disappointed from the RH cluster manager though. all it does > > it move a list of services without dependency on eachother. it's quite a > > lot but it's missing some needed features, like defining a logical link > > or block - service A and B must migrate to new nodes together, but not > > to one that already runs service C for instance. nope, I can only define > > to which nodes each service migrates and that's it. For instance, y > > client wanted a very simple case where three machines run two services. > > if any of the three machines fails, the other two take over the two > > services that need to run, but I can't have both services migrating to > > the same node, and now I cannot prevent this using this tool, I'll have > > to make funny improvizations in the startup files to get it to "fail" > > for the cluster manager and force it to migrate it further to another > > node if this one is busy. this is an ugly kludge, and the only "right" > > solutiong, per RHEL, is to have 4 rather than 3 machines, each pair > > takes care of one service and that it. rediculous :-( > > > > > -- guy "For world domination - press 1, or dial 0, and please hold, for the creator." -- nob o. dy ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
