Shared Cluster Storage - 2 servers can't see files of each other

[Dmitry_31]

Hi
I installed Shared Cluster Storage, connected 2 DL380G3 servers to it (using 5312 SCSI controllers, not built-in 5i). I didn't connect servers to each other using the provided cross-over cable because I don't want to build cluster at the moment. I've created the array and a logical volume on it. Both servers (windows 2000 advanced server installed) can see this logical drive. When I create any file or folder on that drive the other server doesn't see this file or folder and the free space information on that server doesn't change accordingly. But when I reboot this server it can see these new files and folders. What can I do to solve this problem? I'd like both servers to see the files straight after they were placed on the shared disk.
Thank you in advance,
Dmitry

[Vladimir Vybiral]

Hello Dmitry,

I am sorry but this is impossible. Let me explain.
The Cluster Shared Storage is for sharing a block-level SCSI space to servers, You are not sharing a filesystem. The filesystem information resides on the server and is updated everytime You touch the disk from one or the other server. The other server does not know about the update - so he does not know about the new file.
You would need to use some 3rd party application to make it share the space - however, these apps (such as Veritas SANPoint) are designed to work on Storage Area Networks - so they typically do not support SCSI attached disks, and moreover, are priced accordingly to enterprise SAN environments.
If You would use the same space from both servers, the only result is data corruption, as they would be overwriting each other's data.
Making a cluster from the two servers would enable both servers to connect, but one of them would be able to access the disks / the other one is passive. This is done through a quorum disk.
The solution would be to make an active/active cluster (with an application in mind that supports it, eg. Exchange), create a quorum disk and at least two other LUNs, make one preferred to server1 and the second to server2, install the application to both of them and make them able to switch between nodes... here it starts to be quite complicated, let us know if You need more explanation.
hope this helps, though it does not solve Your problem,

Vladimir

[Dmitry_31]

Thank you, Vladimir. We have plans on moving to cluster solution in the future, but for now my goal was to create a redundant storage solution for 2 servers and be able to relatively easy to upgrade to cluster in the future. But when I discovered that 2 servers can see all logical disks in the storage I thought that it might be possible to allow servers sort of 'coexist' on the same disks. But I was wrong. So now I am back to the solution when only 1 server has access to 1 logical disk.
But now I have another related question: Let's assuem that the current config is as follows:
4 disks in RAID1+0 (1 logical disk for Server1) and another 4 disks in RAID1+0 (1 logical disk for Server2). Is it possible to create RAID1+0 using all 8 disks but to configure 2 logical disks there? Will it improve overall performance (there will be more disks available in reading...)

[Vladimir Vybiral · Accepted solution]

Hello,

this is possible depending on the controller. Yes, it would sort of improve the performance for BOTH reading and writing, the problem is when You start a heavy load on one server, the other one would be impacted (as they are using the same spindles = disk drives). You should be aware of that - that is why for fe. DB servers or Exchange You typically do not want to do this, if they sometimes experience a high load and You are not able to tell what the other one will be doing at that time = imagine some high peak on exchange server while the other one would be doing database recovery...
If You still want to try, You have the SA5312 controller, so start the Array Configuration Utility. Delete both Arrays and create just one array, RAID0+1, with 8 disks. Now create two logical drives or units on this array, with the space that You need.
Reboot both servers and You should see two logical drives attached to both of them. You can identify them in disk management, right clicking on the disk and go properties - they have different lun numbers, same port.
To disable access to one of them at each server (You do not want to be asked every time You start the disk administrator for Write Signature, do You ?? :) ), go the Device Manager, select Disk Drives (or Disk Devices or Logical Drives), select the one that You do not want to use on that particular server, go Properties and select "Do not use this device" or "Disable device" on the tab. Do the same with the other logical drive on the other server, rescan disks on both of them and You are up and running, one lun on each server.
I have been pretty detailed - hope this helps, let me know.

Vladimir

[Dmitry_31]

Perfect answer. Thank you. I decided to stay with different disks for different servers.