2011-05-23 12:17 PM
I know that Shared LUNs are supposed to be used only for clustered servers. I'm curious to know why I couldn't use a shared LUN for 2 independent servers that will be interacting with 2 completely different directory structures.
My situation: I have a mail archive service that is split into 2 separate servers. One server houses the database and one server houses the indexes. I would like to be able to store the indexes and the databases in the same LUN rather than carve out separate LUNs for each. Is there a technical problem with doing that aside from it not being recommended. I'm guessing that the recommendation/requirement is based on the fact that you have no way to lock files between two separate servers and could run into data corruption issues. Am I correct in that assumption?
Is there another option that will allow me to use snapdrive and have more than one server connected to a storage unit? (particularly because these are system services so someone may or may not be logged on to that particular server)
Thanks for any input.
2011-05-23 12:49 PM
You are correct that the you would run into data corruption if you had the same LUN attached to multiple servers with no software-level locking (like VMWare, MSCS, etc...) to prevent simultaneous file access.
Have you considered hosting the data as a CIFS volume on the controllers? We had a similar situation as yours come up and we decided the best/only way to allow multiple servers access without clustering software was hosting the data as a CIFS volume on a NetApp controller.
2011-05-23 12:58 PM
I figured that was the case. So, since that's the issue, is there any reason I couldn't share it anyhow since they won't be interacting with the same filesets?
I thought about CIFS but it adds one more level of complexity figuring domain credentials for access to the storage. I don't want anyone else accessing it from the domain but don't want to have to set up domain credentials for those two servers and have to worry about them authenticating/etc. Also, when services run as a local service (which is this archiving product) then domain credentials don't do much since the local service instance doesn't have any network privileges anyhow.
2011-05-23 03:18 PM
I was sort of hoping that this was NFS, then the situation is easy. With Windows, there is no active-active sharing of LUN's anyway unless you use Veritas Cluster Server. Windows 2008 can do NFS, so perhaps this is something to play with. I can't attest to the quality of their NFS implementation, however.
Setting up a CIFS share to be access by a system user isn't that difficult, shares just need to be mapped with a crude "net share" batch script and the filer needs a few lines of configuration. It would be an advantage if it was on an isolated/private (v)lan segment, of course. We run a couple of pretty loaded Notes servers using CIFS shares and it is amazingly stable. There used to be some documentation on NOW on how to set it up, but last I looked I couldn't find it. I have a working implementation, so I have my documentation, in a way.