canuck15 wrote:
>
> I have been looking at the inner workings of Astlinux compared to standard
> embedded applications.
>
> It seems most embedded applications use flash ram as storage but tend to
> load entirely into RAM. The obvious advantages are speed and writability.
> It seems that Astlinux uses temporary folders in RAM and the Kernel always
> loads into RAM by design but Astlinux does not really run entirely in RAM as
> far as I can tell. I was just wondering why it wasn't designed this way
> other than the fact more RAM is needed?
>
Canuck,
I could really go either way on this one. It's certainly open for
debate. The boot CD, for instance, loads to RAM and runs from there.
When loading from CD, you gain a lot of flexibility to run from RAM,
because otherwise you can't write at all!
The problems with running from RAM are many, and a lot of them are
specific to running something like Asterisk:
1) It does use twice as much RAM. As far as embedded solutions go,
AstLinux is actually on the big side. The original PC Engines WRAP
boards (the first board AstLinux ran on) have only 64mb of RAM. That
would be a problem with AstLinux.
2) Running Asterisk. Asterisk writes a lot more that other embedded
solutions. Voicemail, log files, astdb, etc. On something like a
Linksys router, you make changes every once and a while, then save those
changes to memory (usually NVRAM). That way, the device will be
"yank-the-power-cord safe", i.e. those settings will persist even in the
event of an improper shutdown (or in the case of a Linksys router, the
only shutdown). Anyways, the point is that AstLinux had to be able to
somewhat gracefully handle loss of power. You just can't do that
reliably when running completely from RAM. Some things (voicemail,
astdb) have to be committed to disk ASAP.
3) User confusion. There seems to already be a lot of confusion among
users when their changes don't persist across a reboot. Running in RAM
would only exacerbate this confusion. I suppose there could be
something like a Cisco "copy running-config startup-config", but we
would all have to weigh the pros and cons of that first.
--
Kristian Kielhofner
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