Wednesday May 28, 2008

How I found out that I might not exist

Last weekend I got an e-mail from an acquaintance of mine who pointed me to an industry web site where my blog (in particular the mainframe discussion) had been linked - but it said I might be a pseudonym! Read on to see how I got my name back :-) and learned a few things in the bargain.[Read More]

Monday Apr 07, 2008

Don't Keep Your Users Hostage!

Years ago I was taught a formative lesson from response time pioneer Walter Doherty. I asked a (slightly silly) question, and was taught the importance of focussing on service levels. See what I learned here.[Read More]

Monday Mar 03, 2008

The Ten Percent Solution

How do you make a slow, expensive platform look like it's competitive? This is the problem facing IBM with the announcement of their new System z10 mainframe. Read this article to see through deceptive benchmarketing[Read More]

As I was saying

As I was saying[Read More]

Monday Feb 26, 2007

Response to: IBM, Sun and HP: Comparing UNIX Virtualization Offerings

Ken Milberg, a technical editor for IBM Systems Magazine, Open Systems edition, wrote an article comparing and contrasting virtualization technologies from IBM, Sun, and HP. You might not expect an impartial analysis from an IBM publication, but you might hope. Unfortunately, he got a lot of things wrong, both about Sun technology and IBM's. I'll go over some of the mistakes and misleading comments.[Read More]

Friday Feb 02, 2007

Two questions, 1.5 answers...

Two questions (and a partial answer) about when LDoms will be available and whether it requires spending money. I can answer part of that![Read More]

Saturday Jan 27, 2007

And now for something virtually different...

The previous entries describe some of the complex, slow and tricky things needed to implement virtual machines the "traditional" way. This entry gives an overview of how Logical Domains work, and align with CMT architecture, and why they are a completely different approach for low-overhead virtualization.[Read More]

Sunday Dec 24, 2006

Trickiest (virtual) bits - more on why virtual machines are hard to do well

Some parts of making virtual machines work are especially tricky. Read here for discussion of several of the most difficult aspects of virtualization, and how they are handled on different architectures.[Read More]

Tuesday Dec 05, 2006

Why virtual machines are hard

In my entry "Virtual history", I mentioned that some aspects of virtual machines were hard to do efficiently, and then hand-waved over the details. I'd like to spend a few minutes (it's late...) mentioning just a few of the things to be considered. Let's delve into that some now.[Read More]

Thursday Nov 16, 2006

A slight digression with Logical Domains and Apache

Before I carry on describing architectures for virtual machines and other forms of virtualization, a related anecdote driving Apache web server under logical domains (LDoms)[Read More]

Saturday Nov 11, 2006

Virtual history

A little historical perspective on different forms of virtualization, leading (eventually) to constrast with Logical Domains and Solaris Containers (zones)[Read More]

Thursday Oct 26, 2006

It's a virtual world out there

I've finally been tempted to start posting blog entries. Yet Another Form Of Electronically Mediated Communication, but a good one. Most of my posts, at least, the computer-related ones, will be related to server virtualization. It's interesting times now, as a formerly niche technology has become mainstream. As somebody who happily lived for a long time in that niche (mostly in the context of mainframe VM) it's interesting to see a large number of people discover how useful virtualization can be, along with some of the pitfalls you can run into. In a world where there a virtual machines or partitioning technologies on almost every platform (VMware, Xen, Solaris Containers, LDoms, xPars, Virtual Iron and others), you can see people rediscovering issues like nested memory managers (hint: LRU no longer works the way you think). virtual timer management, and other aspects virtualized environments.
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