On the High and Low points of AIX

In the early 1990's IBM recognized the genius in the UNIX philosophy and decided to make their own version, AIX (Advanced Interactive eXecutive?). With a few exceptions, UNIX purists dislike it. I think it has a lot of value, but I usually summarize my feelings on AIX this way:

AIX is a great operating system, but not a great UNIX.

On the Plus Side

From the end-user's point of view, AIX feels pretty much like most UNIX os's: The shells work fine and all of the UNIX utilities are there. Even manpages seem to work, though the formatting is not as clean as in other UNIXes.

From the programmer's point of view, there are a few places where things are not quite the same. Things are better than they used to be: most free software compiles o.k. under AIX, and they're starting to meet up with the API standards for newer things like large file support, etc.

AIX has lots of features that make a sysadmin's job easier:

On the Minus Side

Most of the bad things in AIX all come down to a single problem: The developers at IBM just don't get the UNIX philosophy:

Can You Live With It?

If you're just a UNIX login user, I think you'll be fine.

If you're a sysadmin, you're going to grumble and swear a lot about how different some things are. But there isn't anything so fundamentally wrong with AIX as a system that you can't run a good production shop on it. If you're a relatively inexperienced sysadmin, AIX might even be better, because so much can be managed via menus, and lots of everyday tasks to keep a system running are easier (volume mirroring, backups, etc).

Programmers might find some peculiarities in the APIs, but most stuff is acceptable (basic UNIX syscalls, stdio, signal handling, async I/O, mmap(), etc). The virtual memory system is a little odd (the page table is inverted! You have to walk a hash-bucket chain to translate virtual to physical!) but you shouldn't care.

Managers and the like have a few additional concerns: Solaris truly dominates the commercial UNIX world, so lots of products are developed on Solaris, and then ported to the other OS's. But for most shops, that is not a huge problem. Plus, IBM's relational databases are starting to give Sybase and Oracle a run for their money.

The scary thing is that IBM has been talking about totally revising their UNIX philosophy, and trying to make their systems follow more of the industry standards. Stay tuned.