topic 2 Servers, 1 Volume in StoreVirtual Storage

2 Servers, 1 Volume

HMUSER — Tue, 31 Jan 2012 15:35:27 GMT

I have got 2 servers setup on my SAN network.

I have setup a single volume with access to this single volume from both servers. However it appears that both the servers dont see the same content. There seems to be a delay in the volume updating on one of the servers.

Is there a reason for this and is there a way to stop this from occuring?

The single volume doesnt run network RAID and nor is the servers clustered.

Re: 2 Servers, 1 Volume

bryan_hadzik — Tue, 31 Jan 2012 15:45:28 GMT

What kind of file system is it? Is it vmware, or Xen, or microsoft cluster?

Normal filesytems don't really like 2 servers accessing them. That is that big warning that comes up from the CMC when you add two servers to a volume.

Re: 2 Servers, 1 Volume

HMUSER — Tue, 31 Jan 2012 15:48:59 GMT

Both the servers run Windows Server 2008 R2.

I ignored the warning as i dont want to setup a cluster.

I basically want to be able to view the files on 2 servers as on one server i share out the files so anyone can access the files in the folders and on the other server i use the backup files located on the volume to restore to the SQL server.

Re: 2 Servers, 1 Volume

bryan_hadzik — Tue, 31 Jan 2012 15:59:52 GMT

You can't just ignore that warning, it is there for this exact reason. I would immediately kill the 2nd connection to that volume before you get corruption. Create a 2nd volume, or switch to a cluster.

Re: 2 Servers, 1 Volume

oikjn — Tue, 31 Jan 2012 16:23:35 GMT

++ for the vote for bad idea do not do.

I really don't get the point of the 2nd server. Is this only for backup? This sounds like a small shop setup so I can't imagine you are overloading the server CPU/network by running the backup and the data on the same server.

If this is simply for file shares, why not use the windows DFS-R system that is built in for replication?

whatever you do, don't have two computers writing to an NTFS partition at the same time as it will cause a major problem at some random time... connecting two computers to a LUN is like playing russian roulette.

Re: 2 Servers, 1 Volume

bryan_hadzik — Tue, 31 Jan 2012 16:26:00 GMT

Just to clarify what oikjn said, it isn't a problem connecting two servers to the sam LUN if it is a cluster file system like VMFS.

Re: 2 Servers, 1 Volume

oikjn — Tue, 31 Jan 2012 16:32:35 GMT

true. Thanks for the clairification. That was what I meant.

The rule for EVERY iSCSI target of EVERY SAN is to only connect a single host to a single LUN UNLESS the flie system is something that is cluster aware. IE. you cannot simply make a FAT32/NTFX/ZFS/EXT4/whatever formatted LUN and simply connect more than one host since it WILL cause data corruption at some point. This isn't an HP VSA only rule, its a rule for iSCSI in general.

Re: 2 Servers, 1 Volume

HMUSER — Wed, 01 Feb 2012 10:50:24 GMT

Ok that clears that up then.

Sounds like the way forward is to create another volume and replicate the data from the one volume on one server to the other volume on the other server or just carry on running my SQL restore scripts across the network from the file server with the attached volume.

I assume creating a cluster on the P4000 will just cluster the 1 drive and enable the 2 servers to read/write to the volume?

Re: 2 Servers, 1 Volume

oikjn — Wed, 01 Feb 2012 14:39:28 GMT

Assuming you are talking about creating a cluster under the servers section and not with the VSAs, you are correct. the server clusters there are just to help you keep things organized so that you can make sure axtual external cluster members have consistent access to the LUNs you want and that the CMC won't keep bothering you with warnings that are important if the servers aren't clustered. Creating a server cluster in CMC doesn't make the servers in question clustered... that has to be done on the servers locallay and the CMC "clustering" in that tab is simply for locical orgainzation.

What exactly are you doing? I originally thought this was dealing with network shared folders and backups, is this folders or is this an SQL deal? Either way, unless you are memory/CPU bound, why are you insistent on running these processes on two computers as opposed to one? The application aware snapshot feature can be a great tool for you and most likely scripting something with that is the way to go if your concern is making sure you have a consistent frozen drive to scan.

Re: 2 Servers, 1 Volume

HMUSER — Thu, 02 Feb 2012 09:38:31 GMT

We dont have any VSA as we have not virtualised yet.

If i explain the situation it may give you a better understanding of what we are trying to achieve.

Each night we have a batch file that pulls in data from 40 remote sites. Then each morning we restore the SQL data from the backup to a sql server using scripts to run the sql restore over the network. Now we have got our SAN it will be a lot quicker to restore the data from the LUN using SQL jobs rather than across the network and restore batch files. However we have got other data on the same LUN that users connect to for each individual site.

I think it might be better to move the overnight copy scripts to the SQL server and then create another LUN for the users to access and split the data out. Time consuming but thought i could just share a LUN between 2 servers with out clustering.