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Re: size of "disk cache"




On 23.06.2007, at 08:52, Calvin (Yu-Hui) Liu wrote:
I don't have enough experience on Mac so far. I'm not quite sure if the
"Disk Cache" here refers to "swap partition" as Linux. In my experience
on Linux, I was told to use as same size as the physical memory - 1GB
swap for 1GB memory. "32K for every MB" - it seems to be too small...
What do you think?

This info is for Mac OS 9 and earlier. OS 9 isn't a Linux, it's a pre-Darwin MacOS (what you get when you run a "classic" application on a PowerPC Mac). So, this isn't really on topic for this mailing list, and you may wanna look for another venue to ask your question. That said, I'll try to provide an answer:


The equivalent to Linux's "swap" partition would be "Virtual Memory", which is set up separately, and generally is your physical amount of RAM +x. Since OS 9 is a rather "old" generation of OS design, it didn't remap memory the way Linux did it either. I think the maximum VM amount was 2x amount of RAM.

Disk Cache is usually built into hard disks themselves these days, though OS X does some buffering itself.

Anyway, unless you're into retro computing or have customers or users in educational or DTP settings that haven't been able to move to OS X, you'll just want to ignore any "pre-OS X" information. Classic MacOS is a completely different operating system than Mac OS X. Their only commonalities are that they support a number of the same protocols and file formats, and that some (mostly user-level) applications were ported over. Apple is no longer selling Macs able to run OS 9 or earlier, nor is it selling OS 9 itself. It's a dead product.

Oh yeah: OS X doesn't have a swap partition by default. It just uses the boot volume for swap space. Though you can find instructions on the web how to screw with the config files to get a dedicated swap partition. But that stuff isn't widely used, and not supported by Apple (at least for "regular" Mac OS X -- not sure about Mac OS X Server, and I guess there's some Darwin users who do a separate swap partition, too).

Cheers,
-- M. Uli Kusterer
http://www.zathras.de



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