[OpenAFS] Tuning openafs write speed

[Kai Moritz]

> What are your data rates in MB/s?
scp says: 4.6MB/s

> If you are on a fast network (Gbit Ethernet, Inifiband ...) a disk cache
> may be remarkably slower than the network. In this case memory cache can 
> help.
I haven't tried that yet, becaus in the file /etc/openafs/afs.conf of
my Debian Etch installation there is a comment that says:

# Using the memory cache is not recommended.  It's less stable than the disk
# cache and doesn't improve performance as much as it might sound.

> 
> Another point is chunk size. The default (64 KB) is bad for reading 
> where each chunk is fetched in a separate RPC. with disk cache bigger 
> chunks (1 MB) can be recommanded, anyway. For memory cache of, say, 64 
> MB you would limit the number of chunks to only 64 which is certainly 
> too low.

With automatically choosen values writing a 128 MB file in AFS takes
about 44-45 seconds.
On that machine I have a 3 GB cache.
With the following options, which a have taken from an example in a Debian Configfile, writing the 128 MB file takes about 48 seconds :(

-chunksize 20 -files 80000 -dcache 10000 -stat 15000 -daemons 6 -volume
s 500 -rmtsys

Greetings kai
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