[OpenAFS] poor out of cache behavior on writing

[emoy@apple.com]

On Sunday, February 16, 2003, at 06:36  PM, Garance A Drosihn wrote:

> At 5:01 PM -0800 2/16/03, emoy@apple.com wrote:
>> nfs             0.120u  21.030s  4:19.47  8.1%
>> afs 0.5G cache  0.100u 517.330s 10:49.84 79.6%
>> afs 2GB cache   0.060u  20.570s  4:49.58  7.1%
>>
>> In these tests, I copy a 1 GB file from the client to the server.
>> In both NFS and AFS cases, I use the same client and server machines.
>>
>> Notice that with the 0.5 GB cache, it takes about 2.5x longer to
>> copy the file, and consumes almost 80% of the CPU, mostly in system
>> time.    The 2 GB cache case is more reasonable, taking just
>> slightly longer than NFS.
>
> Notice that your cache is half the size of the file you're trying
> to copy.  In the past we at RPI have noticed that AFS performance
> is bad if the machine has a cache size that is smaller than a
> file you want to work on.

Yes, that was the point; copying a file bigger than the cache.  I  
wanted to confirm that this is expected behavior, especially as bad as  
I am seeing.  I hope this can get fixed someday, because files are  
constantly getting bigger.

Of course, disks are getting bigger as well.  Is there a limit on the  
size of the cache?  I understand files can't be larger that 2 GB, but  
is there some cache size limit at 2 or 4 GB?
------------------------------------------------------------------------ 
--
Edward Moy
Apple Computer, Inc.
emoy@apple.com

(This message is from me as a reader of this list, and not a statement
from Apple.)