Admin had built an application server using the basic dimension guidelines set out in the class he had taken. Notably, the issue had nothing to do with the disk whatsoever. This was about five years ago.
RHEL support got onto the system, did a df, saw the disk dimensions and stated to him that the drive layout wasn't in a supportable layout according to their installation specifications. Call back once it is. *click*. No feedback on what would be an acceptable layout, or anything else. Another admin called in, got the same response, plus they said it must be an issue with the hardware vendor. Called a third time, with both admins on the line, and the same response. RHEL simply didn't want to help out, give useful information, or anything else.
Turned out it was an init script error. I could have seen RHEL support punting at that point, but they never even looked that far into it.
The problem I have with RHEL's (and many other vendors' support, SuSE included) is that they do very well when the issue is clearly defined, they can follow a simple call script in a binder, and you never deviate from that. The problem is that our admins never have to call for those issues. How I rate whether support is any good is when the support doesn't come from a binder.
And I wasn't giving SuSE props for having outstanding support. Their saving grace is that you can pay them to say that CentOS is "supported", because some clients require OS vendor support contracts even if you don't use them. RHEL doesn't "support" CentOS, period. I find that a bit of a detractor, considering there is about 1 line of one file in /etc separating the two distributions from binary compatible operation. It is their choice, but that doesn't mean I have to agree with it.
For the record, I personally haven't called vendor support for a linux issue in over a decade. I've submitted bugs, or additional documentation on bugs, on several occasions but that isn't a support issue. That is me doing their QA work for them, and I won't pay for the privilege of doing that. Prior to that, I'd never gotten a fix for issues I submitted, just an advisement to "wait for the next major release, it might be fixed then". Maybe RHEL has stepped it up in the past couple of years, but I've gone beyond depending up on them or any other Linux OS vendor.