[OpenAFS] Server disk operations speed
Mon, 8 Apr 2013 09:40:50 +0300
> So, I thought that the network communication was the bottle neck,
That is easy enough to test with methods that don't involve AFS or even
disk operations. ttcp, for example.
> but just in case I tested whether it's the server itself that was somehow
> exceptionally slow.
And of course you have other means of testing disk access speeds too that
don't involve AFS or the network.
> I copy/pasted the earlier mentioned test directory
> (see the full message below) first in the normal unix environment
> /home/user/...(source and target), which turned out to be extremely fast
> (HW supported virtualization on a SSD disk). So, no problem there.
My "what exactly did you do?" question was aimed at this. It is not
obvious from your initial message what the steps were that you took to
copy materials, and it is only marginally more apparent from this.
So, what you are saying is that you did something for which it is not
possible to describe the steps as commands on the command line because
they weren't, but rather UI interaction on GNOME or something similar?
(I would have liked to see the commands, that is, and a description of
the sources and targets in each case.)
> Then I got access to an afs account on the same machine (kinit; aklog),
> and copied the same test directory in /afs/cell/user/...(source and
> target) which turned out to be extremely slow.
If I am correct in that you are using the GUI to do this, would it be
possible for you to repeat the test in a way that does not involve the
GUI? In reference to a recent conversation here, it is my experience
that GUIs such as Nautilus etc attempt to analyse the contents and
permissions of the filesystems involved in ways that don't play well
with AFS, and before we come to the conclusion that your AFS server
isn't performing, I'd like to cut out at least one obvious middleman.
> All this took place on the very same server machine, without any external
> clients. I do suspect that in afs case, some traffic _may_ leave the
> machine (use dns to find the external address and return back to the very
> same machine, maybe...), which may explain partly the results.
That would be trivial to observe using any network debugging tools such
as wireshark/tcpdump. Also, if you keep vmstat 10 running on the server
during your tests and post the results, that might be enlightening.
> I'm a bit puzzled since everything works, but annoyingly slowly for
> serious use. Of course my main concern is the speed for clients, not
> within the server.
If you use another client machine and carry out the exact same tests,
is the performance worse / as bad/good / better?
(BTW If you don't mind, I would appreciate it if we kept the conversation
on the mailing list only - I don't need an extra copy in my inbox. Thanks.)