>What exactly do these numbers mean. Netwok data transfer rate, aggregate
>transfer rate.
I recently filed a request with the publications people to get these
summary statistics values explained in the B/A Clients manual, as
while some of them are straightforward, otherse like the Network transfer
rate are complex because of how quickly the network component can buffer
what *SM gives it, though it has yet to even begin moving over the network.
Please - if you see areas of the documentation that need work, by all means
send email to the address provided at the front of every IBM manual.
It's a form of mutual aid that will help keep everyone from having to go
through this kind of inquiry to get fundamental information.
To answer Jack's query, here's the info that I have on these values.
I'd welcome any further insights that anyone has, so that we can all
best understand what contributes to them.
Aggregate data transfer rate Statistic at end of Backup/Archive job,
reflecting transmission over the full
job time, which thus includes all client
"think time", file system traversal, and
even time the process was out of the
operating system dispatch queue. Is
calculated by dividing the total number
of bytes transferred by the elapsed
processing time.
Contrast with Network data transfer
rate.
Network data transfer rate Statistic at end of Backup/Archive job,
reflecting the raw speed of the network,
being just the time it took to transfer
the data over the network.
The data transfer rate calculated by
dividing the total number of bytes
transferred by the data transfer rate.
Contrast with Aggregate data transfer
rate.
Beware that if the Data transfer time is
too small (as when sending a small
amount of data) then the resulting
Network Data Transfer Rate will be
skewed, reporting a higher number than
the theoretical maximum. This reflects
the communications medium rapidly
absorbing the initial data in its
buffers, which it has yet to actually
send. That is, ADSM handed off the data
and considers it logically sent, having
no idea as to whether it has been
physically sent. This also explains why
at the beginning of a backup session
that you see some number of files
seemingly sent to the server before an
ANS4118I message appears saying that a
mount is necessary (for backup directly
to tape), rather than appearing after
the first file. Thus, to see meaningful
transfer rate statistics you need to
send a lot of data so as to counter the
effect of the initial buffering.
Richard Sims, BU
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