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Hosts not seeing the same data on Equallogic SAN

Posted on 2014-07-28
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Last Modified: 2016-11-23
I have a strange issue with my two Dell EqualLogic ps5000 sans and two Dell R710's running Server 2012 R2.

I have set up the two SANs in a cluster, set up a pool with 3 volumes, and presented the volumes to my two windows servers with iSCSI, status shows "connected" in the iSCSI manager.  I have installed the latest Dell Host Integration Toolkit v4.7 to make the software compatible with Server 2012 R2.  The SAN HQ software is also installed.

The volumes are seen normally in disk management and I have formatted them with NTFS using a long format.

The issue that I am having is that when I make a folder and save a file within it, only the server that made the file is able to see it.  The other server looking at the same volume (with the same drive letter assigned) cannot see the file.  When I reboot the servers they are able to see the new files but any new ones are not showing up dynamically.

I also get a message about the recycle bin on drive <x:> is corrupted for each volume.  I tried setting full access NTFS permissions to my account at the root level of the volume I am testing on but still get the error each time I open it in windows explorer. Event log shows this: "A corruption was discovered in the file system structure on volume <X>:. The exact nature of the corruption is unknown.  The file system structures need to be scanned online."

I have also found where the option to "allow simultaneous connections from initiators with different IQNs" can be set on the SANs and it is enabled.

Any help would be appreciated, hopefully someone has run into this issue before and can shed some light on it.  Please let me know if you require any more information from me.

Thank you!
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Question by:bobbailey22
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by:Cliff Galiher
Cliff Galiher earned 500 total points
ID: 40225253
Unless you set up a Cluster Shared Volume (which for file services is not always wise) you can't share a volume with more than one windows node in a cluster simultaneously. Windows clusters are active/passive, not active/active. By allowing both nodes to connect to your volume via iSCSI, you will see anomalies like you described and will get data corruption. Your implementation is wrong.
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by:Max Sando
ID: 40225458
Seconded, it sounds like your windows boxes are separate. You can not run iSCSI the way you described. Why are you trying to host it out in this manner? What kind of data are you putting on this volume?
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Author Comment

by:bobbailey22
ID: 40225623
Thanks for your responses. I am going to be setting up a failover cluster on the windows boxes but have not done so yet.  It sounds like I will need to do that first.  What we would like to accomplish is having two (or more) separate web servers and SQL servers hosting the data on the same storage location.  We already have a load balancer that shuttles web traffic between the web servers.  

That way when we make a change or publish code it only needs to be done in one location.  If one server goes down the system stays up.  There may be more I need to discuss with our developers on the logistics of the IIS/SQL portion but that is the end goal.

Web Server 1
                        >  (central SAN storage for SQL & Web data)
WebServer 2

Thanks again for your comments and help.
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Cliff Galiher earned 500 total points
ID: 40225733
For failover, that's possible. You just don't attach both nodes to the same iSCSI target at the same time. You create the cluster and one node "owns" the storage and is attached. The passive node is in a detached state. In the event of a failure, the passive node will attach at that point.

For load balancing, that requires a completely different architecture that is beyond the scope of a simple EE question, but it doesn't change the answer that two windows machines CANNOT be attached to the same iSCSI target at the same time.
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Author Comment

by:bobbailey22
ID: 40228058
OK sounds good, I will set up the cluster and see how that goes.  I will leave the request open for another week or so in case there are any follow up questions related to the original issue.

thanks again!
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Author Comment

by:bobbailey22
ID: 40244898
It looks like in server 2012 there is a technology called Cluster Shared Volume that allows the SAN storage to be shared and accessed by multiple servers at the same time.  I am reading up on it but it sounds like it would accomplish my original task of sharing the storage between servers.  Is there anything I am missing about that technology?
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Expert Comment

by:Gerald Connolly
ID: 40245365
CSV was suggested by Cliff in his first post.

For a shared volume you need to have some kind of arbitration software otherwise writes from one node will write over writes from the other, thereby causing file system corruption.
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Author Closing Comment

by:bobbailey22
ID: 40247683
Thanks everyone, that points me in the right direction.
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