[OpenAFS] Re: Request at the conference: Configurations used

[Alf Wachsmann]

Dan Hyde of U. Mich. wrote:
> parm /usr/libexec/openafs/fileserver -L -p 128 -rxpck 2500 -udpsize 1048576 -l 1000 -s 1000 -vc 1000 -nojumbo -cb 25000000 -pctspare 1

Harald Barth of KTH wrote:
> parm /usr/openafs/libexec/openafs/fileserver -nojumbo -p 128 -busyat 1200 -rxpck 800 -s 2400 -l 2400 -cb 200000 -b 480 -vc 2400

It turns out that there is an easy and undocumented way of finding out
whether the "-cb" parameter setting is large enough for your file server.

Issue this command aganst your file server in questions:
 	xstat_fs_test -fsname afs106 -collID 3 -onceonly | grep GSS
If any of the GSS counters are _not_ "0" then your "-cb" is too small.
This does not tell you what the right size for "-cb" is, though.

To narrow your search space, consider that 64,000 is the default shipping 
with the file server and that U. Mich. is using 25,000,000.
Derrick's recommendation was to make this number as large as possible 
without causing swapping on the file server.


Here are two examples from our cell at SLAC:

# bos status afs02 -long | grep fileserver
     Command 1 is '/usr/afs/bin/fileserver -L -p 128 -cb 128000 -rxpck 2400 -udpsize 10485760 -busyat 500'

# bos status afs03 -long | grep fileserver
     Command 1 is '/usr/afs/bin/fileserver -L -p 128 -cb 128000 -rxpck 2400 -udpsize 10485760 -busyat 500'


# xstat_fs_test  -fsname afs02 -collID 3 -onceonly | grep GSS
             197130 GSS1
              98565 GSS2
               1308 GSS3
                  0 GSS4
              98565 GSS5

# xstat_fs_test  -fsname afs03 -collID 3 -onceonly | grep GSS
                  0 GSS1
                  0 GSS2
                  0 GSS3
                  0 GSS4
                  0 GSS5


For "afs02" "-cb 128000" is too small, for "afs03" it is fine.


NB: The collection ID 3 is undocumented. If someone can explain to me
what all these numbers mean, I will submit a documentation patch.


-- Alf.

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