Comments on: MSCS confusion http://www.vReference.com/2009/06/18/mscs-confusion/ guides, links and news for VMware and virtualization technologies Mon, 19 Jul 2010 21:24:28 +0000 hourly 1 http://wordpress.org/?v=3.0 By: A Dude http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-903 A Dude Fri, 21 May 2010 13:40:58 +0000 http://www.vReference.com/?p=187#comment-903 This won't work for multiple reasons. As mentioned, snapshots would not be equal for both nodes. In addition, you can't get a SCSI-2 reservation on a delta file (based on how ESX works), and this you'd cause a cluster failover (or worse, a total failure if you tried to do both nodes). This is why vSphere does not let you snapshot disks on a shared scsi bus at ALL. This won’t work for multiple reasons.

As mentioned, snapshots would not be equal for both nodes. In addition, you can’t get a SCSI-2 reservation on a delta file (based on how ESX works), and this you’d cause a cluster failover (or worse, a total failure if you tried to do both nodes). This is why vSphere does not let you snapshot disks on a shared scsi bus at ALL.

]]> By: Forbes Guthrie http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-859 Forbes Guthrie Fri, 16 Apr 2010 20:51:54 +0000 http://www.vReference.com/?p=187#comment-859 Hi Dirk, Firstly, I don't think VMware's MSCS supports more than 2 nodes in the cluster, even if only 2 are virtual (I'm not saying it won't work, just won't be supported). I definitely wouldn't allow any Windows servers to see your regular VMFS datastores. Windows servers have a nasty habit of "initializing" LUNs formated with other file systems. If you want to do this, I would create a special Storage Group just for this MSCS's shared disks (guessing by the name, if this is an EMC Clariion, you can have your ESX server in multiple Storage Groups), and only allow the 2 Windows servers and 1 ESX server to see those LUNs. The ESX server can still be presented other VMFS volumes via other Storage Groups for the local disks. Hope you understand what I'm getting at here, but let me know if you don't. Hi Dirk,
Firstly, I don’t think VMware’s MSCS supports more than 2 nodes in the cluster, even if only 2 are virtual (I’m not saying it won’t work, just won’t be supported).
I definitely wouldn’t allow any Windows servers to see your regular VMFS datastores. Windows servers have a nasty habit of “initializing” LUNs formated with other file systems. If you want to do this, I would create a special Storage Group just for this MSCS’s shared disks (guessing by the name, if this is an EMC Clariion, you can have your ESX server in multiple Storage Groups), and only allow the 2 Windows servers and 1 ESX server to see those LUNs. The ESX server can still be presented other VMFS volumes via other Storage Groups for the local disks.
Hope you understand what I’m getting at here, but let me know if you don’t.

]]> By: Dirk http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-857 Dirk Tue, 13 Apr 2010 11:48:15 +0000 http://www.vReference.com/?p=187#comment-857 Hi Forbes, An additional question to verify how the SAN can interact with all this. We are currently in the migration from a 2-node physical cluster to a 2+1 node (virtual-physical) on our VMWare ESX3.5 U3 infrastructure. The LUN's of the current MSCS-cluster are created on a Logical SAN Storage Group where only the 2 physical hosts are connected. The Storage Groups for our Virtual infrastructure will be used to connect all LUN's. Currently only ESX-hosts have access to this Storage group, but my question is: How will the LUN's (all, including VMFS volumes and RDM) react when also Windows physical machines will be allowed to that same Storage group and see the different LUN's? Hope you can help me with this or give me some insight on how to interpret this situation. Hi Forbes,
An additional question to verify how the SAN can interact with all this.
We are currently in the migration from a 2-node physical cluster to a 2+1 node (virtual-physical) on our VMWare ESX3.5 U3 infrastructure.
The LUN’s of the current MSCS-cluster are created on a Logical SAN Storage Group where only the 2 physical hosts are connected. The Storage Groups for our Virtual infrastructure will be used to connect all LUN’s. Currently only ESX-hosts have access to this Storage group, but my question is: How will the LUN’s (all, including VMFS volumes and RDM) react when also Windows physical machines will be allowed to that same Storage group and see the different LUN’s?
Hope you can help me with this or give me some insight on how to interpret this situation.

]]> By: Forbes Guthrie http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-845 Forbes Guthrie Tue, 06 Apr 2010 23:50:26 +0000 http://www.vReference.com/?p=187#comment-845 I'm afraid my memory of this isn't that clear, but even if it was technically possible its not something I'd ever recommend. I’m afraid my memory of this isn’t that clear, but even if it was technically possible its not something I’d ever recommend.

]]> By: y883 http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-820 y883 Tue, 30 Mar 2010 07:28:26 +0000 http://www.vReference.com/?p=187#comment-820 Hi Forbes If we use phisical RDMs and bus sharing enabled for MCSC(across ESXs), we cannot VMotion VM on ESX3.5/4.0. But I heard that it was able to VMotion VM on ESX3.0.x even if it was used phisical RDMs. Is this correct? If yes, why does not it made? The reason? Hi Forbes
If we use phisical RDMs and bus sharing enabled for MCSC(across ESXs), we cannot VMotion VM on ESX3.5/4.0. But I heard that it was able to VMotion VM on ESX3.0.x even if it was used phisical RDMs. Is this correct? If yes, why does not it made? The reason?

]]> By: Forbes Guthrie http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-742 Forbes Guthrie Tue, 16 Feb 2010 19:28:39 +0000 http://www.vReference.com/?p=187#comment-742 Hi fcorrao, With VI3.5, the virtual RDMs have some advantages like snapshots and potential to use VMotion. There used to be a paper from VMware that stated they recommended virtual mode unless you had a good reason not to (like SAN tools), however I can't find it right now. Interestingly though, with the move vSphere 4, VMware now recommend using Physical RDMs for CAB. Forbes. Hi fcorrao,
With VI3.5, the virtual RDMs have some advantages like snapshots and potential to use VMotion. There used to be a paper from VMware that stated they recommended virtual mode unless you had a good reason not to (like SAN tools), however I can’t find it right now.
Interestingly though, with the move vSphere 4, VMware now recommend using Physical RDMs for CAB.
Forbes.

]]> By: fcorrao http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-740 fcorrao Tue, 16 Feb 2010 14:59:34 +0000 http://www.vReference.com/?p=187#comment-740 Hi Forbes, Your table above lists a cluster across boxes with physical rdms as not recommended, yet the vmware mscs guide that you reference uses physical compatability mode RDMS in its cluster across boxes chapter (ch 3, pg 28). Can you explain your reasoning behind not recommending this configuration? Hi Forbes, Your table above lists a cluster across boxes with physical rdms as not recommended, yet the vmware mscs guide that you reference uses physical compatability mode RDMS in its cluster across boxes chapter (ch 3, pg 28). Can you explain your reasoning behind not recommending this configuration?

]]> By: Forbes Guthrie http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-222 Forbes Guthrie Tue, 27 Oct 2009 22:29:00 +0000 http://www.vReference.com/?p=187#comment-222 Hi Josi, the table above describes 2 different things: - you can create snapshots with virtual RDMs - you can create CAB with virtual RDMs However it doesn't state that you can use snapshots with disks that are used in MSCS setups. If you check the MSCS documentation, snapshots is just one of the things which is not supported on MSCS VMs. Hi Josi, the table above describes 2 different things:
– you can create snapshots with virtual RDMs
– you can create CAB with virtual RDMs
However it doesn’t state that you can use snapshots with disks that are used in MSCS setups. If you check the MSCS documentation, snapshots is just one of the things which is not supported on MSCS VMs.

]]> By: Forbes Guthrie http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-221 Forbes Guthrie Tue, 27 Oct 2009 22:23:48 +0000 http://www.vReference.com/?p=187#comment-221 Hi George, I couldn't find anything relating to tomcat servers and MSCS, but here is a guide to setting up tomcat with NLB: http://blog.paulmcgurn.com/2008/09/tomcat-clustering-on-windows-server.html Hi George, I couldn’t find anything relating to tomcat servers and MSCS, but here is a guide to setting up tomcat with NLB: http://blog.paulmcgurn.com/2008/09/tomcat-clustering-on-windows-server.html

]]> By: Josi http://www.vReference.com/2009/06/18/mscs-confusion/comment-page-1/#comment-213 Josi Thu, 22 Oct 2009 16:14:38 +0000 http://www.vReference.com/?p=187#comment-213 Hi, we try to setup a CAB with a virtual RDM. This works fine - the only think what causes problem is, that we cannot create snapshots from our images anymore, although we excluded the disk from the snapshot processing. We are using ESX 3.5 - is this maybe a version problem? Is this setup only working as described in the table above for ESX 3.0? Any comment would be appreciated. Thanks Josi Hi,

we try to setup a CAB with a virtual RDM. This works fine – the only think what causes problem is, that we cannot create snapshots from our images anymore, although we excluded the disk from the snapshot processing.
We are using ESX 3.5 – is this maybe a version problem? Is this setup only working as described in the table above for ESX 3.0?

Any comment would be appreciated.
Thanks Josi

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