Re: [ClusterLabs] [Slightly OT] OCFS2 over LVM
On 24/08/15 07:55 AM, Jorge Fábregas wrote: On 08/24/2015 06:52 AM, Kai Dupke wrote: Not sure what you want to run on top of your 2-node cluster, but OCFS2 is only needed when you need a shared file system. This is for an application that manages the high-availability by itself (in an active/active fashion) and the only thing that's needed from the OS is a shared filesystem. I quickly thought about NFS but then the reliability of the NFS server was questioned etc. I could create an NFS cluster for that but that will be two more servers. You get the idea. I'm still googling NFSv4 vs OCFS2 If anyone here have experience (going from one to the other) I'd like to hear it. For plain failover with volumes managed by cLVM you don't need OCFS2 (and can save one level of complexity). This is my first time using a cluster filesystem and indeed I get it: there's lots of things to be taken care of many possible ways to break it. Thanks, Jorge Speaking from a gfs2 background, but assuming it's similar in concept to ocfs2... Cluster locking comes at a performance cost. All locks need to be coordinated between the nodes, and that will always be slower that local locking only. They are also far less commonly used than options like nfs. Using a pair of nodes with a traditional file system exported by NFS and made accessible by a floating (virtual) IP address gives you redundancy without incurring the complexity and performance overhead of cluster locking. Also, you won't need clvmd either. The trade-off through is that if/when the primary fails, the nfs daemon will appear to restart to the users and that may require a reconnection (not sure, I use nfs sparingly). Generally speaking, I recommend always avoiding cluster FSes unless they're really required. I say this as a person who uses gfs2 in every cluster I build, but I do so carefully and in limited uses. In my case, gfs2 backs ISOs and XML definition files for VMs, things that change rarely so cluster locking overhead is all but a non-issue, and I have to have DLM for clustered LVM anyway, so I've already incurred the complexity costs so hey, why not. -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ Users mailing list: Users@clusterlabs.org http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
Re: [ClusterLabs] [Slightly OT] OCFS2 over LVM
On 08/24/2015 06:20 PM, Digimer wrote: Cluster locking comes at a performance cost. All locks need to be coordinated between the nodes, and that will always be slower that local locking only. They are also far less commonly used than options like nfs. right. Using a pair of nodes with a traditional file system exported by NFS and made accessible by a floating (virtual) IP address gives you redundancy without incurring the complexity and performance overhead of cluster locking. Then you have to copy all data on the network, which limits data throughput. Also, you won't need clvmd either. The trade-off through is that if/when the primary fails, the nfs daemon will appear to restart to the users and that may require a reconnection (not sure, I use nfs sparingly). AFAIK NFS failover includes an NFS timeout, which can be tuned but might give you an extra time till the failover will be finished by the client perspective. Generally speaking, I recommend always avoiding cluster FSes unless they're really required. Full ACK. greetings Kai Dupke Senior Product Manager Server Product Line -- Sell not virtue to purchase wealth, nor liberty to purchase power. Phone: +49-(0)5102-9310828 Mail: kdu...@suse.com Mobile: +49-(0)173-5876766 WWW: www.suse.com SUSE Linux GmbH - Maxfeldstr. 5 - 90409 Nuernberg (Germany) GF:Felix Imendörffer,Jane Smithard,Graham Norton,HRB 21284 (AG Nürnberg) ___ Users mailing list: Users@clusterlabs.org http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
Re: [ClusterLabs] [Slightly OT] OCFS2 over LVM
On 08/23/2015 03:35 PM, emmanuel segura wrote: please, share your cluster logs config and so on. Thanks Emmanuel. I wiped everyting; reverted to previous known good-snapshot on my VMs :) But it does work indeed as I just mentioned Digimer. -- Jorge ___ Users mailing list: Users@clusterlabs.org http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
Re: [ClusterLabs] [Slightly OT] OCFS2 over LVM
On 23/08/15 04:40 PM, Jorge Fábregas wrote: On 08/23/2015 02:16 PM, Digimer wrote: One, this is on-topic, so don't worry. :) Thanks. Two, I've never used ocfs2 (allergic to all things Oracle), but clvmd makes LVM cluster-aware, as you know. So I have no idea why they'd say that. I just restarted everything and then it worked. I was doing a bunch of stuff so I don't know what really happend. It is working perfectly fine now over LVM. I even extended the logical volume and then used tunefs.ocfs2 -S /dev/vg1/lvol1 and it did the online-resize perfectly fine. Thanks Digimer sorry for the noise! No worries at all, glad you sorted it out. -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ Users mailing list: Users@clusterlabs.org http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
