[tor-relays] Tor relay system & uptime requirements

Steve Snyder swsnyder at snydernet.net
Wed Feb 1 18:59:01 UTC 2012

I'm not familiar with the Sheevaplug, but I have some experience with low-end hardware.

I run a middle node on a Pentium-M 1.8GHz ("Dothan", circa 2004) with 1GB of DDR1 RAM on a CentOS 5.x/i686 box.  I have Tor v0.2.2.x configured for Bandwidth=150KB, BurstBandwidth=300KB.  That 150KB is one-third of my 450KB upload capability.

With this set-up I see the Tor process consuming 2% of CPU, about 60MB of RAM (RSS) used, and I see 100 - 200 connections active at any given time.

That 150KB is the peak traffic that is used (I've never see evidence that BurstBandwidth is used at all).  If fact, it is currently averaging about 90KB.  See here:


The crypto stuff is the CPU bottleneck in Tor, so really Tor's CPU use is gated by OpenSSL's performance.  My CPU, old as it is, has SSE2 instructions and that helps a lot.  I build Tor against a contemporary version of OpenSSL, which doubles the encrypt/decrypt performance relative to the v0.9.8+patches that is standard in CentOS v5.7.


On Wednesday, February 1, 2012 11:45am, "Goulven Guillard" <lecotegougdelaforce at free.Fr> said:

> Hi all,
> I am considering setting up a tor relay.  However my configuration is
> not powerful and I failed to find precise informations about the
> hardware system requirements.  I believe it would be useful to have such
> informations in the FAQ, along with graphs of the needed RAM & CPU as a
> function of the allocated bandwidth.
> Anyway, I would use a Sheevaplug (Marvell 1.2 GHz CPU, 512 MB DDR2 @ 400
> MHz) running Debian Squeeze.  It already serves as a small webserver
> (~200 visits/month, <10 MB bandwidth/month), and 150 MB of RAM are
> allocated to flashybrid (which helps preserving the SD card life by
> keeping /var/log/* and such data in RAM and write it down only once in a
> while).
> First questions : would it be eligible as a tor relay ?  As a tor exit ?
>   Or should I rather go for a bridge ?  I guess my bandwidth will be
> limited by the hardware, how much would you suggest ?
> On the same network is my personal computer which is much more powerful
> but down most of the day, so I guess it would be unworthy to make use of
> it ?
> I have also thought about using the PC of my parents as a bridge
> (smaller bandwidth), but again it is online only a few hours a day,
> would it be worth it ?
> Thanks.
> Regards,
> G.
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