There is a story that salesmen like to tell you: if you buy every piece of your system from them, you'll get excellent support because there's only one vendor involved. One set of people who know everything, one place to contact, and there'll never be finger-point back and forth about whose fault something going wrong is.

This is a myth. Let's look at the reality.

Let's say that you want some front-end servers all talking to a big chunk of disk in a SAN (with hardware RAID-1, over FiberChannel) and backed up by a nice tape silo system. For purposes of illustration, you accept the proposal from a company I will call IMoon. IMoon has their own Unix variant which they run on their own servers, and sure should be able to offer you integrated support for all of this. Except:

• does IMoon make their own disk drives? Hint: no.
• does IMoon make their own SAN controller? Hint: unlikely.
• does IMoon make their own FiberChannel switches?
• does IMoon make the FiberChannel controller cards (ICs included) that they put in their servers?
• does IMoon make their own tape drives? Maybe, at best.
• does IMoon make their own tape silo robotics?

The reality is that no single company makes all of the pieces that go into a complicated server environment any more, especially since the best versions of some of those pieces come from companies that specialize in that narrow field.

While IMoon will sell this to you as an integrated system, while it will have IMoon's badge on everything you can see, and while IMoon will have tested it to a reasonable extent, the reality is that if you have a real problem IMoon cannot really provide 'all in one support'. Because IMoon did not actually make some or many of the important components, it has little or no deep technical expertise with them and thus little ability to provide real support for them in the face of complicated problems.

And almost all serious problems are complicated; the ones where something doesn't work but it's not clear where or why or what exactly is going on. This is exactly when you need that excellent support that the salesperson promised and you aren't getting because IMoon is busy trying to get the real vendor's technical people on the phone or all of the various vendors are pointing fingers at each other or what have you.

Ironically, you are probably better off if IMoon serves as an honest system integrator instead. Then you would have the phone numbers of all the real vendors, and hopefully have support contracts with them (arranged as a bundle through IMoon).

Sidebar: how many IMoons are there?

Not very many. To provide true end to end support a prospective IMoon needs to supply both the hardware and the operating system, for the obvious reasons, which sort of narrows the field down. (I believe there are three remaining candidates, one of which doesn't really sell big servers.)

Companies that just provide hardware and bundle someone else's operating system may be able to provide good support; they may be big enough to get the OS vendor's attention and prompt action, and mobilize a lot of powerful high-level people. But they are not providing end to end support, and they are explicitly at the mercy of the operating system supplier if something goes wrong.

Disclaimer: all examples purely illustrative

I have to say it, but I mean this. This is a hypothetical example that says nothing about either my or the University of Toronto's experiences with real vendors who sell real things to the University of Toronto. The example was picked out of a hat to be complicated and any correspondence between it and any particular real system here is a coincidence.