Can a NetApp volume shared over CIFS be used for Exch 2010 quorum?

I dont see any reason why you couldn't use a CIFS share.

All the stuff I have read indicates the MS will only support a windows OS.  In part because you can leave the directory name blank and have the Install create it and set the rights which can only be done on a windows server with the correct permissions given to it.
That said if you specify both the directory name and server and set the permissions correctly, it should work, as from then on all it is doing is accessing a CIFS share.
http://technet.microsoft.com/en-us/library/dd351172.aspx
If the witness server you specify isn't an Exchange 2010 server, you must add the Exchange Trusted Subsystem universal security group to the local Administrators group on the witness server. These security permissions are necessary to ensure that Exchange can create a directory and share on the witness server as needed. If the proper permissions aren't configured, the following error is returned:
Error: An error occurred during discovery of the database availability group topology. Error: An error occurred while attempting a cluster operation. Error: Cluster API "AddClusterNode() (MaxPercentage=12) failed with 0x80070005. Error: Access is denied."

Sharing over CIFS is not possible but that doesn't mean that you lose the advatages of a Netapp.

With Ontap 7.3.2 and higher you can thin provision and dedupe LUNs, therefore the Single Instance that you lose with Exchange 2010 you regain at the block level with the Netapp

Of course now that we are getting away from shared storage for exchange clusters, MS recomends not having both copies of a database on the same SAN, but having at least one if not both on cheaper local (DAS) storage.  This keeps the SAN from being a single point of failure.

Thanks for the feedback, very helpful indeed. We have a clustered SAN so single point of failure should not be a problem. But I don't understand how to specify the directory name as there are no traditional drives (e.g. C:\) on the NetApp, can one just use the share name (e.g EX14MBXQuorum$)?

Ok, so I took a look at it again and for "Witness Directory" you have to use an "absolute, local, long file path that does not contain ~". How do I successfully supply a CIFS share such as \\host.domain.local\quorum$.

All CIFS shares have a \\servername\sharename format.  I would assume that when you create a CIFS share on you Netapp you will end up with something similar.
Keep in mind that this is not a supported config, as exchange cannot manage the "server" that this share is on.  
 

I do indeed have a CIFS share (e.g. \\host.domain.local\quorum$) ready, but how do I get Exchange to use it? Within Exchange Management Console I have to supply "Witness Server" and "Witness Directory" and it accepts only FQDN resp. "an absolute, local, long file path that does not contain ~". Supplying any form of "\\host.domain.local\quorum$" will generate an error.

Well if you use the host.domain.local for the server and your share name as the directory and it dosn't work, then I guess they are insisting on running it on a supported OS where it creates the share for you.  You could try a share without the $.
Don't you have any other windows server that you could use for this?  Any member server will do.

I see, that's unfortunate as the clustered SAN is the only absolute fail-safe point. Would it be possible to use two FSWs? E.g. both CASHUB-servers.

I understand. I also understand the new road MS is laying out with Exchange 2010 but I thought that if we already have a clustered (and in that way fail-safe) SAN, why not use it.

Good help.