ADSM-L

ADSM/MVS Through Put Responses

1996-12-18 10:46:23
Subject: ADSM/MVS Through Put Responses
From: Paul Jaffray <pjaffray AT EARTHLINK DOT NET>
Date: Wed, 18 Dec 1996 10:46:23 -0500
Thanks to all who responded to my query about through put for ADSM/MVS.
Here is a brief summary of the responses along with what I have found out
by doing some tests.

In a 16Mb/s Token-Ring environment, with WinNT and a 600J, about 2 to 2.5
GB/hr.  In an environment where the smallest link is a 10Mb/s ethernet
connection, reported rates were 1.8GB/hr to 7 GB/hr.  This same environment
also produced twice these rates through a FDDI (100Mb/s) connection instead
of ethernet.  These were the only through put numbers that people offered.
Others offered useful tuning advice (thanks) and information on different
things that can affect the performance such as file size (also thanks).


The next big question was interpeting the information displayed by the
backup client as it does it's work.  If I can sum up the general feeling I
got about these numbers it is that they fall into the category of "Lies,
Damn Lies, & Statistics" ;-).

In order to try and get a better handle on what was going on I started
looking at the SMF records that ADSM was producing.  The SMF records are
cut whenever a client session ends.  The records contain (among other
things):

        Offset  Description
        ------  --------------------------------
        100     Duration of session, in seconds
        116     Amount of backed up files, in Kilobytes, sent to server
        120     Amount of data, in Kilobytes, sent between client and server
        164     Amount of Idle Wait Time, in seconds, during the session
        168     Amount of Communications Wait Time, in seconds
        172     Amount of Media Wait Time, in seconds

After running a few backup sessions I would print out the SMF records and
do the math.  Take the session duration, subtract all the wait times then
divide the amount of data by the remaining number of seconds.  This would
give me a theorectical through put.  It is only a theorectical number due
to the fact that other client activities are not accounted for and it
eliminates the wait time caused by the slow communications interface.

What I found was that by far the largest amount of time was the
Communications Wait Time.  This was due to the 10Mb/s ethernet link on our
3172.  According to a call with IBM, this time should be dramatically
reduced by moving off the ethernet interface on to an ATM (155Mb/s)
interface.

The numbers that I came up with varied quite a bit (not a surprise),
however the majority seemed to be between 3 GB/hr and 6 GB/hr with most the
numbers being in the 5GB/hr range.  This was with client compression turned
on, however I did test with compression turned off and the data rate was
still consistent with the 5GB/hr rate.  All these tests were backing up to
disk however just for fun (?) I did a couple of backups to 3480 tape which
confirmed that 3480 tape sucks (no surprise).


In conclusion, we will likely still go ahead with our plans to backup the
50GB of WinNT data with ADSM/MVS.  We will be changing our 3172 ethernet
card to an ATM card (and hopefully be able to isolate the backup traffic
from other network traffic).  We will also install ESCON attached 3490E
tape drives (no money in the budget right now for more disk space).  With
compression turned on the 50GB of data might only end up as 35GB of data
(30% is consistent with the testing I have done but as always "Your Mileage
May Vary") and with incremental backup the actual amount of data being
backed up should be less than the full 50GB.

As this project evolves I will provide updates to the list.

Again, Thanks to those who responded.
pdj

Paul D. Jaffray
pjaffray AT earthlink DOT net
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