Debian Stable vs Ubuntu LTS for Server?
Well I don't see why people are making a fuss about the quality of the question. It's clearly a decision that lots of developers will want to weigh up before deploying. And there are clearly some differences that are very relevant to deploying each.
I think the prime consideration and comparison between debian stable and an Ubuntu LTS is security and general package updates.
Debian "stable" releases are supported for a year after the next stable release. So if a stable comes out every two years, and you started on a stable release right at its launch, you get three years of updates:
The security team tries to support a stable distribution for about one year after the next stable distribution has been released, except when another stable distribution is released within this year. It is not possible to support three distributions; supporting two simultaneously is already difficult enough.
You should note that the debian cadence is not guaranteed. Stable releases come out when they're ready. This could mean you get anywhere from 18 months to 18 years of support. This makes it very unpredictable as you won't know when you need to upgrade until you know when the next stable will be finalised.
Compare that to a Ubuntu LTS release, desktop updates are very similar but for the server applications and kernel, you get a mammoth 5 years of support, regardless of any new LTS releases in that time:
A new LTS version is usually released every 2 years. With the v12.04 Long Term Support (LTS) version you get 5 years support for both the Ubuntu Desktop and the Ubuntu Server. There is no extra fee for the LTS version; we make our very best work available to everyone on the same free terms.
This means you should be able to deploy the latest LTS on a box and not have to worry about it not getting security updates (for supported packages) for years and years. When you have more than a handful of servers, or just some applications that can't afford any downtime for testing upgrades, or just don't have the time to spend a day/week testing upgrades, Ubuntu has a large advantage over debian.
To answer your question about Professional/Production use I think there are several key elements that have been addressed but there is one point I feel that is extremely crucial.
Packages and Package Management
This is a key difference between Debian stable and Ubuntu LTS especially if your concerned about longevity, uptime, stability etc.
Ubuntu is released every six months and is based off of the Debian unstable branch which generally means overall newer and more up to date software but at the same time having the disadvantage of being considered basically "unstable" at least in an enterprise context.
Now the LTS release is based mostly on Debian Testing which in Debian terms "represents the state of the upcoming stable release before it is actually considered stable" and although Ubuntu puts a lot of time and effort into making regular and LTS versions as stable as possible after the packages have been pulled from there respective Debian branches, LTS is still based on the Testing branch which in turn is still considered by Debian in its own branch to be not quite ready for Production use or anything approaching mission critical.
And Ubuntu's community of developers simply cannot compete on the same scope or level of Debian which is possibly the largest communal based software ever created.
In basic terms this means Ubuntu LTS being based upon the Debian Testing branch and even with Ubuntus attempts to stabilize and polish their testing packages after they're pulled, does not equal the immense development and maturity of Debian stable and the packages thereof. Debian stable truly is the Golden Standard for rock solid stability.
I stumbled upon this thread whilst googling "ubuntu server stability issues" - searching for answers to my own concerns regarding the stability of Ubuntu server.
I have to admit that I'm a long term Ubuntu fan, particularly on the desktop (Since Breezy).
Box 1: "Fred"
I first deployed Ubuntu server 8.04 on a production machine that has low usage requirements; it's predominantly a "brochure-ware" level webserver with about 4/5 websites, which also acts as an offsite backup repository. Primary packages are Apache2, Mysql, Postgresql, PHP.
It's dual core, has 2 GB RAM, 2x 1GB HDD configured with mdadm as RAID1. Stability wise, it has been great except that it seems to die every 3-6 months for no obvious reason, despite combining through log after log.
I've kept this machine on 8.04, performing occasional updates.
Box 2: "Charlie"
Charlie has been running for a similar lifetime as Fred, and is used as an office based backup and media storage machine, office server monitoring node, network gateway for remote logins, wiki and virtualbox host. Primary packages are: Apache2, postgresql, mysql, PHP, webmin, samba and Virtual box - Non OSE (We needed the headless feature back when that wasn't supported in the OSE).
Hardware wise, Charlie is Quad core, with 8GB RAM, has about 10TB of storage, distributed across a number of sata and ide drives, some of the sata drives comprise a soft RAID5 array, we have a drobo connected over firewire, two external usb drives and another drobo due to be attached.
Charlie started on Ubuntu 8.04, has been upgraded periodically via dist-upgrade and is currently at 10.04.
Sadly, Charlie is as stable as drunk in a brawl.
Charlie has frequent kernel panics, OOM's and requires a reboot every 2-3 weeks. Combing through logs has me scratching my head.
To Summarise
I love Ubuntu server, it's familiar, relatively well laid out, I love aptitude (Which should be the default package manager IMHO, packages/apps such as UFW, Fail2Ban, Denyhosts, logwatch, logrotate etc make administration relatively simple.
But both Ubuntu server boxes have uptimes measured in weeks or months, if we're lucky, and yes, during that time we've changed the hardware and re-installed from scracth, tested the disks, tested the RAM.
By comparison, I have clusters of HP DL360 G5's, DL380 G5's, DL380 G6's where uptime is measured in years, sometimes, 1000's of days.
These are running CentOS - and it doesn't float my boat like UBuntu Server, but it seems so much more stable, yet I don't know whether that's the Hardware or the OS.
Just my two-pence worth.