[OpenAFS] Re: Performance issues

Jaap Winius jwinius@umrk.nl
Wed, 24 Aug 2011 01:10:04 +0200

Quoting Andrew Deason <adeason@sinenomine.net>:

> What approximate throughput are you seeing in the two cases? ...

I've been monitoring bandwidth usage with Cacti, which shows that even  
internal throughput does not normally exceed 3 Mbps. The graphs for  
the main Internet connections are pretty much the same and the  
available bandwidth is almost never maxed out. It's probably safe to  
assume, however, that there are lots of spikes that don't show up in  
any of these graphs.

> ... I would guess that this has more to do with the bandwidth and
> latency, but unless there are more dropped or reordered packets or
> something, I'm not sure either way what we would see from the OpenAFS
> fileserver point of view besides worse bandwidth/latency.

After both the fs and db servers were moved from the virtual hosts  
(and from behind the firewall and NAT) to the bare metal, we saw a  
marked improvement in local performance. For example, certain  
applications, particularly the Iceweasel (Firefox) browser, only  
became usable after the fs server was moved. But as I said, after the  
changes we've seen no performance improvement for when the user  
volumes are accessed remotely.

(It has been interesting to note that, when dealing with poor file  
server performance, we found Chrome and Epiphany to work far better  
than the two other browsers we tested, Iceweasel and Opera.)

I'm now leaning towards the idea that latency is the main factor  
slowing down our remote performance. Latency becomes more important as  
protocols become more chatty, and I've not been surprised to see AFS  
described as being such. When combined with the use of GUI desktops  
(even lightweight Xfce) instead of simple shell environments, that's  
not going to improve performance either. Originally I was hoping the  
AFS client cache would do more to compensate, but I guess that was a  
bit too much to expect from it.