Do you have any good or bad experiences to share running SQL Server OLTP Systems on NetApp appliances? I have been working with a small, relatively low-volume cluster with a lower-end NetApp device, and I have found the environment to be generally unstable, at least compared to my experiences with other SANs, iSCSI arrays, and DAS setups. I struggle to believe that RAID DP and WAFL are more than fairy-dust technologies. A solution has been proposed to me that I just need a bigger, better NetApp, with PAM cards and other cool technology I've not heard of, and I feel like I would be better off spending a quarter of that on good direct-attached drives and a beefy server. At the same time, I feel that an Enterprise-class SAN should be something I can count on to be consistently a more stable, better performer than the less expensive solution I might propose. Are you a SQL Server DBA in an OLTP environment and love your NetApp? If you don't like them, why not?
SQL Server will not (or at least would not fairly recently) work off a SMB shared volume as SMB does not support the necessary file locking semantics. You will need LUNs exposed through iSCSI, FC over Ethernet or Fibre channel to do this. If you're using the NetApp as a Filer sharing SMB volumes this could be the source of your problem.
Buy a SAN if you want SAN features (snapshot backups etc.) otherwise buy the direct attach storage. If you really just want a box running SQL Server to support a portfolio of apps with moderate load a single big SQL Server box with direct-attach storage will probably work fine. It will be cheaper, faster and probably cost you less in SQL Server licencing.
For some values of big, a bog standard two-socket Nelahem box like a DL380 G6 will probably qualify. This will cost you two sockets worth of SQL Server licencing, comes with 8 cores and takes up to 192GB of RAM. It can take 16 disks internally and you can attach 100 or more externally with stock controller and external shelf (MSA70) options. Most other vendors offer a box of similar spec.
If you're using SQL Server EE, the machine and a DR box will probably cost less than the SQL Server licencing for two sockets. If you're starting small, populate just one socket and save yourself $20k or more on the licencing.
I think this type of box is underrated and getting more so these days - as VMs and blades are all the rage now. However, this is a seriously powerful machine capable of supporting a pretty agressive database workload for just two sockets worth of SQL Server licencing. If you're currently on a low-end SAN, this will cost less and run rings around it for performance.
If all you care about is running MSSQL in a cluster then I'd suggest you'd be far better off going for a dedicated 8Gbps FC array - certainly if performance under load is a main concern and bottom-line price is less of an issue. Obviously if you don't need clustering then CoTW's post above makes a strong argument for DAS (I love MSAs too ;))
We're mostly a HDS/HP-XP and HP-EVA house but we still have LOADS of NetApps boxes around purely because they're a really good compromise. Having a single box that's often better-than-good-enough at all those protocols can be a real boon. That said in my opinion they don't do FC/FCoE anywhere near as well as dedicated boxes and aren't much better than OpenFiler etc. for iSCSI/NFS - I also think that they're a swine to setup from 'bare metal' if you have a reasonably complex environment. But there's no denying that NetApps look great value to many people, I just have my doubts personally.