I think the only difference is the paid support.

Well, it's a bit more than that.

[ul]
[li]The binary RPMs from Red Hat are the ones that hundreds of hardware and software vendors certify against. That is an important difference when you are troubleshooting.[/li]
[li]The control of the RHEL roadmap is in Red Hat's hands. There are only a few ways to influence that roadmap. You can work in Fedora, as many CentOS people do, or in other upstream projects directly, and let that trickle down to the next RHEL release. Or you can be a customer and have your product managers work on it for you.[/li]
[li]When it comes to working with upstreams on the behalf of customers, Red Hat has the longest and greatest record in this industry. If you are prepared to work on your own behalf in any upstreams that matter to your business, then you have one way to keep control of your future. Another is to have Red Hat do it for you.[/li]
[/ul]

Interesting that the question of "RHEL or CentOS?" is often discussed on both sides as a matter of cost. When you look at it further, you find there are legitimate reasons to decide either way, depending on your needs and resources.

It comes down to the requirements of your organization/company. If you have a support (i.e.SLA) requirement, then you would be wise to use RHEL. However, CentOS can suffice for any needs that come from the use of RHEL. You would have to decide on the requirements of your company/organization.

If you do have a hiccup <which will eventually happen> you need to make dang sure that you have a plan to CYA if you are not using RHEL.

If you are familiar with the CentOS / Red Hat relationship, you probably wouldn't say so much. It is not just built from the SRPMS. FYI, CentOS is widely used in the financial industry for the servers that run many co-located trading platforms used by the market makers at the NYSE, NASDAQ, CBOE, and other major exchanges world wide. These are systems where high reliability is essential since a few seconds of downtime for algorithmic derivatives trading can run up loses of million$. A company I used to work for developing risk analysis software develops, manages, and sells as a service the quoting/trading/hedging software used by most of the market makers and professional options traders at the CBOE. They migrated all their servers to CentOS last year.

woboyle wrote:

If you are familiar with the CentOS / Red Hat relationship, you probably wouldn't say so much. It is not just built from the SRPMS.

Can you clarify what you mean by these statements?

FYI, CentOS is widely used in the financial industry for the servers that run many co-located trading platforms used by the market makers at the NYSE, NASDAQ, CBOE, and other major exchanges world wide.

Yep, I'm sure it is, as is RHEL itself. I recall when NYSE switched to RHEL:

http://searchenterpriselinux.techtarget.com/news/article/0,289142,sid39_gci1316018,00.html

These are systems where high reliability is essential since a few seconds of downtime for algorithmic derivatives trading can run up loses of million$. A company I used to work for developing risk analysis software develops, manages, and sells as a service the quoting/trading/hedging software used by most of the market makers and professional options traders at the CBOE. They migrated all their servers to CentOS last year.

Actually, I'm a bit surprised at this. Considering that the RHEL technologies seem to be at the core of that business, why would they move themselves farther downstream?

Perhaps they are embedding their own developers directly in the upstreams that matter to them? Or they don't understand what open source truly is about and why it is better software?

My experience is that the financial services companies are interested in supported software, and some of them also understand the open source model intimately. For example, JP Morgan decided to open their code to gain the advantage of an open source collaboration and an open standard (http://www.infoq.com/news/2008/08/amqp-progress). The resulting open standards working group (http://amqp.org) was formed by AMQP's originator, John O’Hara, and when he wanted that group and mission to grow, he got Red Hat involved. From the reference implementation (http://qpid.apache.org) to Red Hat MRG (http://www.redhat.com/mrg/), Red Hat been involved in making this open source project successful.

Could John O'Hara have turned to the CentOS community for that work? Perhaps. Instead, I suspect that community would have told John to talk with Red Hat.

The three reasons to run RHEL (from my experience):

1.> You have third-party software that requires RHEL for support purposes.

2.> You have hardware that is exotic, and requires cooperation between RedHat and the hardware vendor to make things work, or fix problems down the road.

3.> You would rather manage machines instead of actively administrate them (for whatever reason).

I have worked for an organization that had to use RHEL for any one or combination of those three reasons. We also used CentOS on all development machines (much more Linux friendly than some of the production hardware we used), and for our own in-house servers.

You can purchase support contracts from Red Hat for CentOS now. Also, I know a number of major software vendors in the financial trading markets (stock and options exchanges) that run CentOS on their trading/quoting servers that are co-located at the exchanges, such as NYSE, CBOE, etc. Personally, I think the choice is 6 of 1 and a half dozen of the other. So, a lot of the decision is going to be related to executive "comfort level".