RHEL 6: serious Linux built for growth
Excitement? We've heard of it
Review Red Hat has released Red Hat Enterprise Linux 6, the first major update for RHEL in over three years.
RHEL 5 debuted in March 2007 and used the Linux 2.6.18 kernel. Although incremental updates have added a number of kernel updates and new features, RHEL5 is starting to look aged. Of course much of the appeal of an enterprise distro is precisely that it ages well - ten years in RHEL's case.
This means that, for all the appeal of what's new in RHEL6, 5.x will still be supported for another seven years.
That longevity also helps to explain some of the new features you'll find in RHEL 6. For example, the staggering hardware capabilities - on 64-bit platforms, RHEL can scale to 128 cores and 2TB of main memory.
Some might find it strange to support systems that don't exist at the moment, but when you consider that Red Hat will still be supporting RHEL 6 in 2020, it starts to make more sense.
RHEL takes the long view and that means starting from a rock solid foundation and supporting systems that don't yet exist.
The latest and greatest GNOME not featured here
One of the main goals for RHEL 6 was to make managing virtual servers as easy as managing physical machines, which means the bulk of the new software features in this release are found in KVM. It also means that Xen is gone, though that's hardly surprising since Red Hat purchased Qumranet - creators of KVM - back in 2008.
RHEL 6 builds on the KVM-based virtualization found in RHEL 5.5 and earlier releases, adding a number of performance and hardware support upgrades. Upgrading from old Xen-based disk files is also simple, just boot KVM and point to your Xen loopback disk files and reboot your virtual machines.
Also new for virtual guests is the SELinux sandbox feature, which allows guest machines to run in isolated environments. The new sandbox features can be applied to just about any untrusted code you'd like to execute but is particularly handy with virtual machines.
Big disk options
Another big change in RHEL 6 is the wide selection of disk formatting options, including ext4. You know a Linux feature has arrived when it makes its way to the conservative enterprise releases like RHEL and such is the case with ext4 file system, which is now the default filesystem format in RHEL 6.
In addition to ext4, the XFS filesystem is now supported.
As with previous versions of RHEL, the Anaconda installer offers a variety of pre-configured sets of software packages depending on your needs. For the workstation release that I tested, there were options for the Gnome desktop, a "minimal" desktop, a web development workstation and a software development workstation as well as the bare essentials available in the "minimal" option.
There is also an option to customize your installation further, selecting individual packages. For testing purposes we started with the basic GNOME desktop package, adding the server platform, along with common tools like MySQL, PostGRES, FTP server and e-mail server, as well as the new virtualization tools.
While the RHEL desktop is perfectly usable, if you're a casual desktop user looking for the latest and greatest new toys in Gnome or KDE, RHEL isn't the distro for you - you're better off with one of the many free Linux distros available.
Next page: Desktop to server
Having multiple kernels is good thing.
Same kernel can work from laptops to clusters, but it will not be top performance everywhere. That is true for every OS. Microsoft HPC server and Vista 7 don't run same exact kernel, at least compile flags are different.
Different RHEL kernels usually are not that different, just compiled with different optimisations enabled, and to make top performance Red Hat ships different kernels for different uses. Otherwise, customers will download source and compile their own kernels to achieve maximal speed, and if that happens, updates might brake the system since Red Hat used different flags.
"I think it is funny that you doubt there will be a 16.384 thread Solaris box in 2015."
Keb, I have no doubt that there will be a Gazillion threaded Solaris box in 2015. I guess you can get one right now.. a Exadata with 32 four socket nodes.. that is 32 x 4 x 128=16.384 Threads..
"You know, when Sun did the 8-core Niagara that was shocking."
Jup it had shockingly bad single threaded throughput...
"But Sun has always been a leader, and others have followed. "
Oh they have ? In what way ? Please enlighten me ?
"Now everybody (in particular IBM) has stopped the GHz race and turned to many lower clocked cores - just like Sun did ages ago."
Nahh.. that is not the whole story. POWER7 still clocks in between 3GHz to 4.25GHz, and that is with an increased per core throughput. A POWER 595 with 5.0 GHz cores does 33.75 specint_rate2006 per core where as a POWER 795 with 4.25 GHz cores does 48.05 specint_rate2006 per core. Now that is a 15% drop in frequency for a 42% increase in throughput.
With regards to Oracle's Tx it's just more threads and more threads... so get real. Sure the increased work done per socket is good for throughput, but it still requires workloads that can be scaled horizontal. And here real life problems like locking becomes a serious problem on many workloads.
"And Solaris scales well. Which AIX does not, they had to reprogram AIX to be handle to handle as few as 256 thread machines."
First you are wrong with the threads thing, counting a problem ?
I think you have misunderstood the concept of scalability. It's not an advantage to have many threads if they don't do much work.
And that's with almost x3 better response time.
It's the work done that matters not the number of light threads.
"Solaris is the correct tool for a 16.384 threaded monster server. The performance will be shocking."
Well you are talking about something that is what 3-6 Generations into the future. Again in the future...
Not a practical problem.
Yes I guess that the T3 then finally puts Linux on SPARC in the grave, as a serious platform.
And 128 threads is more than enough for the sweet spot of Linux. I mean that is a 8 Socket Nehalem-EX box with Hyperthreading enabled, a 16 Socket Itanium and a 4 Socket POWER7 box. Sure with todays virtualization, what this actually mean is that you have a max. virtual machine size of 64 cores on x86, 64 cores on Itanium and 32 cores on POWER7. Which is kind of enough.
And in 2015 we'll all have flying cars and live forever.... yeah... right..