DIAL comparison of NFS and dcache
David Adams
December 28, 2005

To compare NFS and dCache performance, I processed a 
large AOD sample (6000 files, 30 GB) reading from NFS
and reading from dcache. I also ran jobs building the file
lists (replica resolution, etc.) so I could subtract that
contribution to estimate the processing time. The time for
merging is not subtracted.

I ran 35 jobs simultaneously.

NFS uses two disks data08 and data12 served from separate
servers, file03 and file04. Earlier test using a single
disk magdacache003 from file02 showed much worse
performance.

Results are in the following table:

        Total   File   Proc  bandwidth
         time   time   time  MB/s fi/s
        -----  -----  ----- ----------
NFS     12:10   3:05   9:00    50   10
dCache  27:30   3:55  23:30    20    4

Doubling the number of subjobs had a small effect on the
total time. NFS decreased, dCache increased.

The ATLAS application runs at about 2 MB/s so a total
throughput of 70 MB/s is required to run 35 jobs
simultaneouslyi at full speed.