Shared Storage Problem

Question

Hi All,

I am facing problem while asigning one LUN to one storage group. That storage group has three hosts but when we put data on that LUN and try to see that data on all three hosts it shows it on one. When we restart remaining two hosts then we can see our data on them as well. DATA also got corrupted.

Need assistance....

Thanks & best Regards,

Abdullah Khan

Kiran3 · Accepted Answer

what we are trying to tell here isthat you cannot share your lun on 7 hosts like this.each windows server needs to write a signature on the disk -> some specific bytes in the begining of the disk so that it can keep track of disks.if a disk is detected on server and the signature is not identified, the server shows the disk as unallocated. in your case, when you open disk manager and ask windows to write signature, each windows server tries to write its own signature and filesystem, this creates confusion and corrupts data.

Kiran3 · Answer

you can only share a lun with multiple hosts if the hosts have an arbitrator software to control who can access the lun. this is usually a cluster software.

xe2sdc · Answer

Every host will keep it's 'vision' of your data in its cache .. When you dismount the filesystem every host will push its cache on the drives, corrupting what other hosts already did in the past. If you need to mount a single filesystem on different hosts, think about using a Network Filesystem (NFS on unix and CIFS on windows). A single host will see the disks on the storage and will export the filesstem/shares to the other hosts.

Dulls · Answer

Hi,Thanks for your replies. I would like to add some more in detail:WE HAVE:RAID GROUP 1 under that Raid Group there is one LUN.Storage Group1 under that Storage Group we have 7 Host running Win2K3 Ent.We assigned that one LUN to Storage Group1.On one host when we format that Assigned LUN, it successfully done. On remaining host when we open diskmanagement it shows unallocated disk.Please advice...

xe2sdc · Answer

Please note that the signature is simply the tip of an iceberg ..
When you have a cluster you CAN have the signature written from one node and "imported" in the other node of the cluster ..

Even if you don't look at the tip of this iceberg, you'll have to face some more difficult problems, like the cache that every host uses while working on drives (as per my previous example) ..

Could you please explain what you want to do ?? Maybe we can help you

Dulls · Answer

Many thanks for the reply. What I am trying to do is, I have 7 servers in one storage group and want all LUNs to be shared by each server in that storage group. So they can shared all the data which stored on the LUNs.

No requirement of Cluster.

Bowling1 · Answer

Windows does not support what you are trying to accomplish.
Microsoft does not support presenting the same lun to multiple servers without some kind of clustering software - Symantec, MSCS, etc.

What you need to do is Implement a NAS solution to support file sharing.
You could also potentially "share" out a lun from a single host and present the Share to the other servers - Poor man's NAS solution if your application allows it.

xe2sdc · Answer

You already have your answer .. you need to SHARE data between 7 hosts.. You don't need a storagegroup with 7 hosts.. you need a single host in the storage group. And you need to share the lun via CIFS (microsoft way of sharing folders) between the 7 servers. This is -as someone else said- poor-man's nas .. but it works .. Even if it have a big (huge) single point of failre: the single server in the storage group.

johncorne · Answer

To increase availability, cluster the servers offering the CIFS share.Jc

xe2sdc · Answer

Yep it's a simple task .. but will require a thing that seems to be missing since the beginning .. a cluster

CLARiiON

Shared Storage Problem

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