[Asterisk-Users] SUCCESS - 512 Simultaneous Calls with Digital Recording

[trixter http://www.0xdecafbad.com]

On Wed, 2005-09-21 at 10:07 +0300, Zoa wrote: 
> The reason i recommended you to use a ramdisk is because i think the
> problem with recording to disk is saving 20ms of stream 1, then 20 ms of
> stream 2, then 20ms of stream 3 etc etc.... meaning you write everytime
> very small things. (with a lot of seeking).
> Our best test results were with:
> 
filesystems are also a consideration with larger scale projects.
Different filesystems add different amounts of overheads on different
types of operations.  Some are faster at moving small files around
others faster with large files.  This adds to the disk latency.
Removing the disk latency itself is a good thing, since that is
typically slower, but to crank out that last little bit of performance
some research into the different filesystems under the specific kernel
that you are using could also be a consideration.  The most obvious
(and easiest to update a running system) is to remove things like atime,
whih with most linux distros is on by default.  This causes a write
operation for the read of a file to update the last time accessed.  A
couple little things can add up to a few percent improvement and
generally make the cost go down.


> - buffering the recordings to a ramdisk, then
> - on low load (at night) copy the files over the network (easy to shape
> the pipe, so that you dont overload anything), 
Or have a seperate network set up (dual nic card for example) where the
2nd network is used just for NFS traffic.  Although NFS generally is
ugly network wise, it is standard and makes things easier.  Just gotta
watch the IO on the system given that the network card itself will cause
cpu cycles to be used, but lets face it cpu is cheap now.  Different
drivers also work differently, and then with the 2.6 series kernels you
can use device polling instead of interupts which can help a little.



> If you want to go even freakier, run asterisk (or you complete distro)
> from a ramdisk.
> 
When you say ramdisk here I assume you mean using conventional ram, its
cheap yes but its volatile, do you have any plans for failure of the
system or ram?  Or is the data integrity itself not as critical?  The
reason that people like hard drives is because most of the time if the
system goes down for any reason the data is still intact.  


> I thought over your suggestion to use a sniffer to do the recordings,
> you might pull it off, but will have to write your own to do so. (or go
> to the expensive version of commercial sniffer applications).
> 
isnt vomit free?  It was a voip sniffer that worked with some codecs
many years ago (I wanna say mid-late 90s but I may be thinking of
another back then). http://vomit.xtdnet.nl/ does G.711 only.

The bigger prIoblem that I see is that sniffers dont always get all the
traffic that is on a network particularly when the network has more
traffic on it.  While this generally isnt a concern and I would like to
think that even a poorly configured network could allow for 512 calls,
it is a factor to implement this type of a solution.

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
UK +44 870 340 4605   Germany +49 801 777 555 3402
US +1 360 207 0479 or +1 516 687 5200
FreeWorldDialup: 635378
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