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Clustering on Windows 2003

Posted on 2004-11-02
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Last Modified: 2013-11-15
Here is my sisutuation , I currently have a Windows 2003 SE server which is the main server in my organization. I also have a newly deployed Exchange Server 2003 running on Windows 2003 EE. I also have a 2000 Server that is not doin anything. My plan is to upgrade that server to 2003 EE as well as my main server, and implement a 3 node cluster using the old server as the common media device as it is my undeerstaing that you have to have one in order to utilize clustering. Several question I have regarding clustering are:

1) In the event of a server going down will clustering allow me to utilize that third server to run my apps in the interim?
2) What kind of Software will have to be installed on that common media device? I asume 2003 EE, but do I need to have a separate set of CAL's for it even though it would only be used in the event of an emergency?
3) Do I need to install all of the apps that I would like it to run in the event one of my main servers (Exchange & File server) goes down?

I have had several vendors come in and pitch software such as Legato to me, but if clustering can perofrm all of these functions without using a third party app then I am inclined to go with that as the solution. Your feedback is greatly appreciated.
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Question by:Nolanb2004
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    by:Chris Dent

    You won't get too far with the other server as shared storage unfortunately. Network Attached Storage isn't supported just yet (which is what the third server would be).

    The Shared Storage device in a Cluster (with Exchange) must be mountable prior to the System Attendant starting. That gives you a choice of SCSI Attached Storage (probably a drive array) or Storage Area Network (either Fibre Channel or iSCSI).

    Clustering is always an expensive one...

    If you had a shared storage device available then the answers to your questions are:

    1. In Active / Passive configuration it would allow a Cluster Transition onto a Passive Node with a downtime of a few seconds (while the transition occurs).

    2. The common media does not have any software installed, it's just a common drive. It will store things like the Exchange Databases and Transaction Logs. A Quorum disk is also used to store Cluster Information.

    3. Each Node in a cluster must have a full installation of each piece of Software required to run over the Cluster. This software must also be licensed.
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    by:Nolanb2004
    Wow! That puts a major dent in my plan! So in other words the apps on my main server would also have to be installed on my Exchange Server and vice versa? They would also have to be full blown versions with seperate licensing and cals? Also, what exactly is a Quorum disk?
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    by:Chris Dent

    The Quorum Disk is a shared (and generally small) disk area that holds the information about the cluster itself. It has to be held somewhere so it's always available really. It's possible to set it up with a Local Quorum disk, but not something I'd advise.

    Yep, the apps would have to be installed on both Nodes in the Cluster (including Exchange). Of course you still need to find a shared storage device to that lot ;)

    Licensing is seperate for the Server applications and Operating Systems (you'd need one per node), but the Client Access Licenses don't need to be duplicated if you opted for (as almost everyone does) per seat licensing.
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    by:Nolanb2004
    OK this my estimation what I will need:

    (1) Server 1: Exchange Server 2003, Exchange CAL's, Windows 2003 EE, Main App, Main App Licenses (actually using the same Main App CAL's from Server 1),
    (2) Server 2: Exchange Server 2003, Exchange CALs (actually using the same CAL's from Server 1), Windows 2003, Main App, Main App Licenses
    (3) SAN: Does not need any software (is this correct?)

    What if i used the same copy of my apps for both servers(Exchange, Main Apps, etc)? I would still intall separate copies of Windows 2003.
    Now this Quorum Disk could be part of the SAN right? What would the configuration of the SAN look like?

    Jeez, now I see how Bill gates got to be the richest man in the world! The way this is looking it going to be unbelievably expensive.

    Thanks for your comments!
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    by:Chris Dent

    Correct...

    SANs aren't exactly the cheapest things in the world though.

    So I'd ignore that one really and consider a SCSI Attached Storage Array. Many of those will have support for clustering. Last time I bought one of those it was something like £6000 for a 300Gb storage array (that would store the Quorum Disk as well as all the Exchange Databases and Logs).

    You could use the same copies of the apps for both servers, but you would of course still need seperate licenses.
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    by:Nolanb2004
    OK so I could attach both servers to one SCSI Storage Array? I need to have separate licenses for all of my apps as well? Just so I understnad this, on my e-mail server Exchange will be running as usual. Why do I need to have another copy of it on another server and a seprate storage device? I'm confused to how this works. It seems overly complicated. Is it?
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    by:Chris Dent

    Not only do you need seperate licenses but they have to support Clustering.

    Yep you can attach two servers to one array provided the array supports it of course.

    Exchange will need to be installed on both nodes in the cluster if you want that to failover. Never tried running it on only one node in the cluster.

    The Storage device itself only stores the Databases and Log files, or anything else you want to be always available.
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    by:Nolanb2004
    Hmmm, good point I have to confirm that our main apps support clustering. I'm going to do that now. If they don't I might have to rethink my plan. On a side note what would be your recommendation for Disaster Recovery. As I mentioned in my first post, I have had several consultants in that have proposed third party apps that will replicate the data and provide failover support. One is SHI, the other is Legato, ever heard of them or do you know of any that are real good?
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    by:Chris Dent

    SHI no, Legato yes but I've never used it personally.

    There's also Veritas and Arcserve for Backup solutions, my favourite would be Veritas.

    Windows doesn't really have any exceptionally good backup support (ntbackup is pretty basic). Of course there's the hardware associated with that one too.
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    by:Nolanb2004
    3 questions regarding clustering:

    How diffcult is it to set up?
    How realiable is it?
    Can clustering on Windows 2003 support co-location?

    Thanks in advance.
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    by:Chris Dent

    Moderately difficult I suppose.

    Reliability depends on hardware as well, so pick the most likely thing to fail and that defines the reliability of the cluster. What clustering does it try to protect you somewhat by giving each node (server) in a cluster an alternative. Still, if your shared storage breaks every 5 minutes then it won't gain you all that much.

    Yes, geographically distributed cluster is possible (I think 3+ nodes), but that needs very careful planning, dedicated connections all over the place and can get very very expensive.

    What are you trying to achieve though? MS Clustering is a nice option, but it's certainly not a cheap one. So you may find investing is a very good backup system and suffering some short downtime in the event of system failure is much more worthwhile.
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    by:merowinger
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    by:Nolanb2004
    Good article, thanks for all the info guys, keep it coming! Would you know if some of the issues experienced with Windows 2000 AS Clutering have been addressed in Windwos 2003 EE? To answer the questions from the Chris, right now I do daily backups of my two servber using Veriotas Backup Exec. Wokrs great and have been able to restore from them with rrealtive ease. However I am interested in having some king of contingetncy plan in the event I have a hard drive crash, etc as I have had in the past. Granted, I have 4 hour response contract with my hardware vendors, but that still is 4 hours that my network will be down. There are several software vendors such as NSI's Doubletake, EMC's Legato and Computer Associate has a what seems like a pretty good solution too. But all of them are reasonably pricey and clustering has been another option I have been considering. I had a consultant in yesterday and he was also mentionin Windows Virutal Server as well. Does anyone know anything about Windwos VS and how it compares to Clustering or is it not even in the same boat? What do you guys think about the whole idea of a having a failover/ data replication system and what would you do?
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    Well it all really comes down to money really. If you can't afford lots of equipment then I personally believe you'd be better seperating Applications from Network Services (like Domain Controllers). Then thinking about fault tollerance on the Application Servers themselves and splitting those onto their own servers.

    It's not, perhaps, as fault tolerant as a full blown Cluster, but it spreads the load of the services around and simplifies any rebuild task - which arguably is more important than creating a single very complex system which could plausibly take a day or more to rebuild.

    It would make for a few more servers, but the system as a whole would be much harder to break. Something reasonable would perhaps be:

    Domain Controller 1 - This one runs DHCP, Schema Master, Domain Naming Master and PDC Emulator. It also runs a secondary DNS Server and Global Catalog. The server itself is relatively low spec, but has it's system disks mirrored with Hardware RAID.

    Domain Controller 2 - This one runs RID Master and Infrastructure Master. It's also the Primary DNS Server for the Domain and Global Catalog. As with Domain Controller 1 it's relatively low spec, but still has mirrored system disks with Hardware RAID.

    Domain Controller 3 - Well you can add as many as you want, there's a reasonable limit really dependant on the number of clients you're looking after.

    Application Server / Cluster 1 - This is the Exchange Server, it does nothing else other than Exchange and it's quite a powerful server. It might be a Cluster to give total server failure fault tolerance. As with the other servers it runs a Mirrored disk set on Hardware RAID for it's system disks.

    If Exchange Databases and Logs are held locally (SCSI Attached Storage (or Shared SCSI Attached Storage) or Internal Disks) then Logs are placed on a pair of Mirrored Disks, Information Stores on a RAID 5 array. Plenty of disk space is included to cope with expansion.

    If the Exchange Databases are held on a SAN then the SAN must, at the very least, run RAID 5 disk sets. Using either iSCSI or Fibre Channel Interfaces. The SAN also has another version of itself which mirrors all the data from the first.

    Because it does nothing more than Exchange the restore procedure is pretty simple, expected downtime being only a couple of hours in the case of serious software failure.

    Application Server 2 - This one is the Backup Server, it's responsible only for performing system backups. As with the other servers it uses Mirrored system disks.

    Etc etc, now no single failure is going to cause the domain to die, no single failure is going to render all applications inaccessible.

    In all of the above servers we're protected against a single hard disk crashing. Exchange is one of the more difficult ones to provide failover for, but a single cluster running everything is too much of a complex system to be reliable.
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