Does anyone have any experience of the Ibm DS3400 san. Have found a system with about 30 servers connected to it (mostly virtual machines including all the operating system drives) including 2 sql servers (1 in very heavy use) and one exchange server. I have had a look at IBM's website but can't find any guidance on what is acceptable on this device.
SAN performance has so many variables involved that I can understand why people don't get into them too much.
Any given SAN has main components that contribute to it's limitations, they are;
I'm lucky, I often get to build SAN arrays for a single purpose - either fast as hell for DB work or big for video content or back - I have the luxury to get separate systems for each function but every so often I need to build something that covers a bit of both, here's what I do;
If you plan out your systems in this way you'll see gradual, not steep, predictable performance drop-off as you add servers and load. Obviously you don't mention any details of your array or usage pattern but there are situations where a single server could saturate a DS3400/NetApp and there are situations where literally thousands of servers would leave the same box with oceans of capacity left - it really does come down to system design and understanding your usage patterns.
Feel free to come back to us when you have more data.
Does NOT depend on the number of systems but on what they do. SQL + exchange are heavy users. Especially SQL can use a LOT of discs to run properly (as any database), but again totally depending on what you do. I ahve seen a SQL Server with 190 dedicated discso once. My own one is on 6 discs now, upgrading soon.
I dont think - besides a technical limit - a guidance here is possible on general terms.