Solaris

Yes, you continue to bring up a point which is a red-herring - you still, using your own words "do not get it".

You take one of a couple of alternatives, because you seem to love swap, for some reason, which is a legacy leftover from the days of expensive memory; and then you try to justify your position by insisting to dump in swap.

You continue to stand on that position, and continue to toss out unconvincing arguments to justify a position which is not accurate.

This is called "fallacy" and in this case, you create a red-herring fallacy to distract from the orginal point, attempting to prove you are correct because you scored a point on the red-herring, which is really not germane to the discussion.

Believe me. You do not need swap in most modern systems. Swap slows you down - why do it with memory is cheap. You don't need to dump in swap either.

reborg's orginal statement on this was not misleading; and that was the only reason I jumped into this thread.

I don't think I ever wrote or suggested I loved swap. Swap isn't something to be loved or hated but something that need not be undersized.

To properly size the swap area, there are two factors to take into account.

1: at the peak virtual memory consumption, all memory reservations need to be backed by either RAM or swap area pages. This doesn't means any activity will necessarily occur on the swap, just the pages have to be there. Solaris isn't doing lazy memory allocation like the Linux kernel does. The free virtual memory can be easily monitored and it is easy to increase its size by adding new swap devices or swap files, so this first point isn't that much of a problem.

2: The default Solaris configuration is to have crash dumps to be written on the swap. Many (but not 99.9% of) Solaris installations are using this standard configuration. In the old Solaris 2.x days, the swap area was very often larger than the RAM size because the (already obsolete) rule of thumb x2 was still followed. There was no risk for the crash dump not to fit. Nowadays, it is not uncommon to have the RAM much larger than the swap. That means there is a risk to miss the invaluable data stored there should a panic happen. I'm not telling this risk cannot be overcome, I'm telling many people are unaware of this risk because it is not common to monitor the kernel size and even less common to check if it would fit in the dump device should a panic occur.

Swap doesn't slows you down, lack of RAM slows you down when swap is available and crashes your application when no swap is there. I strongly prefer my applications to slow down and the OS to paginate than seeing random applications crashing because of malloc failures.
There are also usage profiles were using disk instead of RAM to store virtual memory make sense. If a process, say a whole SunRAY user session, isn't going to be used for days, what is the point keeping its data bits on RAM ? Better to use that RAM as file cache for live applications.
RAM is cheap, true, but disks are definitely cheaper.

Indeed but the issue is most people do it because it's the default.

Perhaps did I pick the wrong word. I don't say the statement is incorrect, I just say that statement would deserve some explanations. I have met several unexperienced Solaris administrators who wrongly thought the crash dump was directly written to the savecore directory. On the other hand, I'm glad Reborg enlighten us about the undocumented way to save the dumps on an UFS file.

jlliagre,

You are playing with semantics.

Swap slows you down because it is used instead of RAM..... we don't need to play semantics.

As folks agree, let's move on.

(1) The 2XRAM rule of thump for swap is a legacy artifact from days gone bye bye. RAM is cheap.

(2) There is no compelling reason to use swap if you invest in cheap memory, you will have better performance.

(3) There is no compelling reason to use swap for dump space. If you must dump, you have other choices than swap.

That is all that we have been saying. This is the days of very cheap RAM. Use RAM not swap is what reborg and I have been advising - and in defense of this position of "Use Cheap RAM Not Swap for Better Performance" we were sidetracked with a red-herring argument about dump and swap.

Honestly, you are an unwitting champion of fallacy, (you use a lot fallacy in counterpoint) because you just did the same thing with your statement:

"The default configuration for Solaris is to dump in swap." This sets up another fallacy to many readers that there is something "good" in default configs.

This point is simply another fallacious argument, because there little inherently "good" about default configurations. If so, we should all leave the root password blank, which is also a default configuration in some systems; or leave the IP address 10.0.0.1 (or what ever it is, etc), or we should leave our hostname... etc etc.

My point is a friendly one. You have great technical ideas, and are a strong contributor, but you support your good ideas with logical fallacies. I don't think you mean to do it; but you use fallacy in your counterpoints, and this is something that annoys me when *anyone* does it. Also, it distracts from the core discussion, because we have to deal with fallacies, which defies logic.

If you had of not reacted so strongly with fallacy to reborg's list, but instead commented without a fallacy in your rebuttal, I would have never joined it, as I don't do this as much as I did 10 years ago .... I leave it to the everyday system admin guys like reborg whom personally manages more servers that most could imagine!

In other words, keep up the great work, but learn to see what is fallacy and when you use it in your debate points, and then evolve toward not using fallacious logic or implications. Wikipedia is a great place to learn the basics.

I'm not playing semantics. I'm afraid you failed to read or understand my points but I give up trying to explain further. I never intended to reach such a locked situation. Thank you anyway for your time.

So, I will close the thread and refer you to Wikipedia:

List of fallacies - Wikipedia, the free encyclopedia

I really suggest you understand fallacy and logic, because you are doing as a lot of technical people do, when you are in a technical debate and you want to make a point (perhaps to win, be correct, etc) you resort to flawed logic, logical fallacies.

It does not matter how correct you "think you are", you basically took an alternative configuration and used at least two forms of fallacy to justify your position.

PM if you want do discuss further, or we can open another thread on "Now to Avoid Fallacy in Threads and Posts"... which I think I might write anyway, now that this topics has my attention here and elsewhere.

PS: I am trying to teach you about fallacy in logic because I like you :-)