________________________________ From: Digimer <li...@alteeve.ca> To: Zama Ques <quesz...@yahoo.in>; linux clustering <linux-cluster@redhat.com> Cc: Rajveer Singh <torajveersi...@gmail.com> Sent: Thursday, 3 January 2013 10:47 PM Subject: Re: [Linux-cluster] GFS without creating a cluster On 01/03/2013 10:22 AM, Zama Ques wrote: > ----- Original Message ----- > From: Steven Whitehouse <swhit...@redhat.com > <mailto:swhit...@redhat.com>> > To: Zama Ques <quesz...@yahoo.in <mailto:quesz...@yahoo.in>>; linux > clustering <linux-cluster@redhat.com <mailto:linux-cluster@redhat.com>> > Cc: > Sent: Thursday, 3 January 2013 3:46 PM > Subject: Re: [Linux-cluster] GFS without creating a cluster > > Hi, > > On Thu, 2013-01-03 at 18:00 +0800, Zama Ques wrote: > > Hi All , > > > > > > Need few clarification regarding GFS. > > > > > > I need to create a shared file system for our servers . The > servers will write to the shared file system at the same time and > there is no requirement for a cluster . > > > > Planning to use GFS but GFS requires cluster software to be > running . My confusion here is If I just run the cluster software ( > cman etc ) without creating a cluster , will I be able to configure > and run GFS2. Also , is it possible to write to a GFS file system > from many servers at the same time ? > > > > Will be great if somebody can clarify by doubts. > > > > > > Thanks in Advance > > Zaman > > > > > > > If you want to use GFS2 without a cluster, then you'll only be able to > > use it from a single node (just like if you were using ext3 for > > example). If you want to use GFS2 as intended, with multiple nodes > > accessing the same filesystem, then you'll need to set up a cluster in > > order to do so, > > Thanks Steve for the reply . As you said setting up a cluster is > needed to use GFS2 with multiple nodes, does that mean that I need > to create cluster.conf or running cluster services (cman etc) should > be fine for setting up GFS2. Not sure whether cman will run without > creating cluster.conf > > Assuming that I need to setup cluster.conf in order to use GFS2 , > that means if there are two nodes in the cluster with GFS2 as file > system resource , GFS2 will be mounted on only one host based on > failover domain policy . But our requirement is like that GFS2 > should be mounted on both servers at the same time . Based on my > little understanding of GFS , looks to me that I will not be able to > achieve this using GFS2 or there are some way to achieve this ? > > Please clarify on this. > > > Hi Zama, >> As steve said, you must have to configure proper cluster to use GFS2 > filesystem and mounted on multiple nodes at the same time so that all > can > access it. You do not need to configure GFS2 filesystem to be > managed by cluster i.e. rgmanager. but just make the entry in /etc/fstab > file as like > normal ext3 filesystem. >> I hope, it answers your question. > > Thanks Rajveer for clarifying . I think I am clear now . Will now try to > configure GFS2. > > > Thanks > Zaman > Note that you will also need proper fencing setup (usually using the > nodes' IPMI interface). Without properly configured, tested fencing, the > first time a node fails the GFS2 partition will hang (by design). > The reason the cluster is needed is that the access to the shared > storage and file system has to be coordinated between the nodes so that > one node doesn't step on the other. This is possible thanks to DLM; > distributed lock manager. DLM uses the cluster communications, hence the > need for the cluster. > Note also that you need shared storage, obviously. iSCSI or DRBD if you > only have two nodes. > Please take a look at this link. It explains in details how this works; > https://alteeve.ca/w/2-Node_Red_Hat_KVM_Cluster_Tutorial#Concept.3B_Fencing Thanks Digimer for pointing the need of proper fencing setup . After configuring GFS , I did power down on one of the node and could see that the GFS mount point got hung on the other host as you have pointed out . Will now try to add fencing to the cluster. We are using HP Storage works for shared storage and accessing space from it using multipathing. Thanks Zaman Thanks Digimer.
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