[rhelv6-beta-list] My first experiences with RHEL6 beta

[Bryan J. Smith]

John Summerfield <debian at herakles.homelinux.org> wrote:
> rsync is the only program I've seen that can use extravagant
> amounts of virtual memory and not cause thrashing.

It's not rsync, but block cache/buffer operations.  Throwing blocks
around is what eats up memory, buffers writes, caches what is written.

Tunables such as read-ahead, swappiness, vm.dirty*, etc... can greatly
affect performance -- an order of magnitude or even more!

I know there was a recent patch to the kernel so swappiness can be
tuned to a fraction (below 1), which is becoming a reality for systems
with 256GiB to 1TiB+ of memory.

> I will only speak to _my_ usage. Some of the assumptions
> behind RHEL seem to be a poor fit for environments I work in.

Discussing the merits of different distributions is yet another
theoretical, meta-type discussion.  People are free to have them,
but people do have real systems and most things don't apply.

However, I will say one thing ...

There is a huge difference between a sysadmin who knows how to tune
an Enterprise Linux, and one that does not.  _No_ distribution can
come "pre-tuned" for all applications.  So it is really not about
the distribution, but what the sysadmin knows to do with it.

I'm a long-time Debian fanboy, former maintainer and, in general,
I try my best to keep up-to-date with Debian Stable devleopments.
I'm also a long-time "ports" (BSD, now Gentoo's "ports on steroids"),
with publication credits (and even share publication credits with
Gentoo's founder).  I also run into plenty of Canonical-Ubuntu.

I've yet to see any distro, out-of-the-box, do everything for everyone.
In fact, installing another distro almost always accomplishes _less_
than just learning the distribution, and setting it up and tuning it
proper.

I've seen Red Hat consultants and engineers tune, patch and do all sorts
of things both upstream and, at request, another distribution.  _Knowing_
and _understanding_ Linux, especially the kernel, especially the tunables,
is what matters.

That's why Red Hat offers classes like RH442.  Even if you don't believe
in certification, I always and highly recommend RH442 to really get into
the internals of Linux.  Real "theory" paired with actual "tools."

And Red Hat continues to be the greatest concentration of Linux experts.
Ones that everyone taps -- upstream, customers, even people who run other
distros.  So one might say ...

  "I will only speak to _my_ usage. Some of the assumptions
   behind RHEL seem to be a poor fit for environments I work in."

And I'll merely reply ...

  "Red Hat offerings are a concentration of enterprise solutions
   knowledge, experience and other, customer feedback.  They are
   not perfect out-of-the-box, but Red Hat has never about selling
   a shrink-wrapped product and waving goodbye.  ;)"

I'm, of course, very biased.  But that too is based on watching
Red Hat professionals for about a dozen years now, including
many times as a customer, let alone independent consultant with
a client.  ;)


-- 
Bryan J  Smith             Professional, Technical Annoyance 
Linked Profile:           http://www.linkedin.com/in/bjsmith 
------------------------------------------------------------ 
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