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

Rich Sudlow rich@nd.edu
Sat, 24 Apr 2010 16:39:39 -0400

On Mar 26, 2010, at 2:22 PM, Holger Rauch wrote:

> 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
> from 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 our cell we typically see write speeds of 60 - 85 MB sec  on
gigabit clients (with no client tuning).

You mentioned that your network connections are Gb capable - but are  
set to Gb?? Your speeds are typical of a client with 100 Mb network  


> (In case I forgot to mention something, please don't hesitate to ask).
> Thanks in advance!
> Kind regards & have a nice weekend,
>   Holger