Monitor the SSA-disks being backed up, you should be happy if you can
read > 6MB/s out of a single disk-drive. So the single-disk-drive
throughput is the bottleneck. To improve throughput try with with
multiple sessions.


        -----Original Message-----
        From:   Matthew Emmerton [SMTP:Matthew_Emmerton AT AGORAINC DOT NET]
        Sent:   Wednesday, May 27, 1998 2:19 PM
        To:     ADSM-L AT VM.MARIST DOT EDU
        Subject:        Performance Issues

        We're running ADSM 3.1 on an RS/6000 R50 server (4x604e) with
~150 GB of
        SSA DASD, of which ~60 GB is being backed up daily.  We're using
a 3590
        drive as our backup device.  Oh, and it has 2 GB of RAM.


        These are some older statistics (when we were backing up
less...)

        Total number of bytes transferred:  36.02 GB
        Data transfer time:                 5,616.98 sec
        Network data transfer rate:         6,724.53 KB/sec
        Aggregate data transfer rate:       1,348.57 KB/sec

        How I am interpreting this is that over the network (TCP/IP,
100BaseT
        Ethernet) I'm getting ~6.5 MB/s (around 65% utilization) which
is
        acceptable.  However, the aggregate (as I'm interpreting it)
would be the
        overall throughput of the system.  Now, according to the 3590
        documentation, it should be able to back up at up to 9 MB/s.
The SCSI-2
        bus driving the 3590 can handle at least SCSI-1 speeds of 10
MB/s.   The
        SSA driving our DASD can handle well over SCSI-2 speeds; so the
drive and
        network I/O don't seem to be the limiting factor.

        What I'm wondering if there is not enough iron behind the ADSM
server,
        which is causing the performance problem - that is, why we can
only back up
        1.3 MB/s when all of the subsystems can handle more.  We've
tried all kinds
        of performance optimizations on our TCP/IP settings, as well as
using over
        512 MB of RAM for ADSM cache, with minimal performance
improvement.  We've
        tried the stuff in the ADSM Performance Tuning Guide (v3) and
the folks
        from IBM don't seem to have any clear-cut answers.

        What I'd like to know is if a) anyone else has had similar types
of
        performance problems and b) what is a decent typical backup
speed?  Am I
        being too ambitious in wanting ~9MB/s?

        --
        Matthew Emmerton, System Administration
        Agora Food Merchants, National IT
        +1 (905) 565-4231