Best OS for NAS, Downloader, Media Server, VDR

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hedgegee replied at Sun Apr 5, 2015 16:34
I think you are correct tkaiser - maybe with the tweaks you posted somewhere in the forum would he ...

I wouldn't call that tweaks exactly. Sometimes it's just about the age of the distro base one is using.

Raspbian for Bananas has been developed by the LeMaker guys and basically they just merged a Raspbian base image for the RPi with the necessary kernel stuff for A20 (the Banana's SoC). At that time the default 3.4 kernel for the A20 used the 'fantasy' CPU governor which clocked the CPU cores really weird (based on 'fantasy algorithms' maybe?) and so especially single thread performance was really bad (explained here in detail). After some investigation this has been fixed in the official Raspbian distro from LeMaker. But maybe not in cyryllo's OMV image? Therefore this would be the first thing to check. And it's also important to check the contents of the fex file (script.bin) used since some conditions are set here (it's the board's initialisation file for older kernels)

Same applies to general network settings. The A20 is so slow compared to x86 PCs and all the network stuff has to happen directly on the CPU cores (there aren't offload engines and stuff like that present on every better PCIe network card) that it makes really a difference whether network tunables are adjusted for Gbit networking or for lower speed networks (as it's normally the case with A10/A20 boards).

And then both network and I/O performance scales almost linearly with CPU frequency. So each and every benchmark for a A10/A20 based device posted somewhere is rather useless when the CPU frequency (and governor!) is not mentioned. Since it makes a real difference. Unfortunately this even applies to some kernel config parameters (A20 has 2 CPU cores and so SMT/process scheduling becomes important). And so on.

As a starting point regarding CPU frequency and network settings I would recommend reading from here on: http://forum.lemaker.org/forum.php?mod=redirect&goto=findpost&ptid=8312&pid=38582. There's a pastebin.com link containing the cpufreq stuff. And regarding network settings tuning the sysctl values outlined here might be a good start. All this stuff can be adjusted at any time in a shell window. And when the results look nice then it's time to put it into a startup file (eg. /etc/rc.local -- no idea whether that's used on Raspbian)

Edited by tkaiser at Wed Apr 8, 2015 06:22
cyryllo replied at Sun Apr 5, 2015 09:03
In free time I will try to test the new kernel.

BTW: I would try out Igor's image with mainline kernel (and maybe decide later to put OMV on top of his image). Some network/NAS/Samba performance relevant stuff has been discussed in the meantime in another thread here with some useful links at the end of the thread.

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