[OpenAFS] Some questions about AFS

[Jeffrey Altman]

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Anders Magnusson wrote:

> - What are the actual limitations on users/groups/volumes/sizes?  I'm 
> interested in both
>  practical and theoretical.  I have tested with 200k volumes/partition, 
> which seems to
>  work fine with the exception of that zapping volumes take 12 seconds each.

The max partition size is 2TB.
The max volume size is 2TB.

>  I also added 200k users and 200k groups, and tested access groups with 
> 200k people
>  in each, without any noticeable slowdown.  Quite impressive :-)   I 
> don't know if or how  any problem here should be noted.
> 
> - What are reasonable maximum on files/directory and 
> mountpoints/directory? 

The max number of directory entries of 15 character names is 64K.  A 15 
character name only requires the use of one block in the directory. 
When names get longer additional sequential blocks are required to store 
the name.  Each additional block provides an additional 32 characters of 
name.

In real world use the maximum number of objects is somewhere between 
16,000 and 25,000 depending on the average name length.

> I tested by
>  adding 64k mountpoints (volumes) in one directory, and accessing 
> directories below did
>  not become noticeably slower.  The only peculiarity I noted was that 
> Windows explorer
>  only showed the first 1000 entries, but I don't know if it is a bug in 
> explorer or the AFS client.

The Explorer Shell will try to evaluate the contents of each mount point 
before displaying the entry.  It may be that you simply didn't give it 
enough time to do so.  I have test directories with more than 10,000 
items that are displayed in full and \\afs\andrew.cmu.edu\usr\ is a 
particularly harsh test case as it is a directory full of symlinks to 
mountpoints to volumes

> - A few problems with the windows manager tools were also noted, it may 
> be just me that
>  haven't really understand how it all works :-)
>    In the server manager; running salvager failed with the error messages:
>       The AFS server manager was unable to perform the requested salvage 
> operation.
>       Error: unable to successfully read log file (0x0000422A)

You aren't running the AFS Servers on Windows.

In any case, the Server Manager tool is not particularly well supported 
and in my opinion not very well designed.  Do not make your evaluation 
of OpenAFS based upon the existence of this tool unless you are will to 
sink development resources or money into its replacement.

>  Also, moving volumes do not work, but I get no error message.  
> ``nothing happens''.
> 
>  The AFS account manager do not start for me at all, it just hangs with 
> "Querying; please wait...".

The AFS Account Manager is "kaserver" and the tool is designed for 
managing the server running on Windows.  You are using Heimdal as your 
KDC and you are not running the servers on Windows.

> I must say that we are all very impressed of how well it has worked so 
> far!  Great!

Glad to hear it.

Jeffrey Altman


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