[OpenAFS] Why is speed of AFS loopback adapter set to 10 Mb, even if physical interface is Gb capable?

Holger Rauch holger.rauch@empic.de
Fri, 26 Mar 2010 19:22:48 +0100

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Hi everybody,

I installed OpenAFS for Windows 1.572 on a Windows 7 Professional (64
bit) system with all system updates applied in conjunction with
Kerberos for Windows (KfW) and the Network Identity Manager. I
downloaded all packages from Secure Endpoints' web site. The PC is
consists of current HW (Intel Core2Duo, 4 to 8 GB RAM, etc.).

Unfortunately, the maximum transfer speed on Windows is about 8-10
MB/sec when I copy local files to an OpenAFS volume. All involved
network components are gigabit capable and I don't experience this
problem when doing file transfers to a native ext3 filesystem using
scp, for example. (I consider this comparable since the transfers are
encrypted as well, in case of SSH/SCP even with a much stronger
encryption algorithm).

The server is a Debian Lenny system running OpenAFS 1.4.11 obtained
=66rom the Debian backports repository. The system is a QNAP TS-809 Pro
with an external HD for the OS. The QNAP HDs are Seagate 7200k RPM
drives of the Enterprise series used with SW RAID 5, totalling 6,4 TB
in capacity. OpenAFS volumes reside on /vicep partitions which in turn
reside on Logical Volumes (LVs). (We're only 25 users, so this scheme
works perfectly well and has the advantage that the size of the
underlying LV implicitly determines the quota, so I don't have to
worry about setting OpenAFS quotas).

The questions are thus:

- Can I change the speed of the loopback adapter on Windows 7? If so, how?

- Why does the loopback adapter's speed default to 10 Mb instead of
  the speed of the physical interface (Gb) at all?
- What's a "normal" transfer speed for OpenAFS when run in gigabit
  network environemnts?

(In case I forgot to mention something, please don't hesitate to ask).

Thanks in advance!

Kind regards & have a nice weekend,

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