On 02/02/2012 04:18 PM, Alan Adams wrote:
You've picked up one of the biggest problems with respect to deploying
software to laptops. In general they are only turned on and connected
to the network when the users want to work on them, and pushing
software out to them in the background can cause problems.
It is a particular problem in schools. A typical scenario is that of
30 children collecting laptops, taking them to the classroom and
switching them on. At this point there is a lot of network traffic
associated with Group Policies being deployed. As soon as the login
window appears they enter their credentials, and there is another
burst of GPO traffic.
Somewhere in the middle of this wpkg starts downloading the 45MB MSI
of Adobe Reader. Not content with that, it uninstalls the previous
version, so it downloads that MSI as well.
You've now got 30 laptops downloading 100MB of data each across, in
the best case, 2 33Mb/sec wireless shared links. 30,000 mbits, through
66mbit/sec is 500 seconds, about ten minutes, ADDED to the normal
startup and login time. Add the contention and retransmission overhead
when the wireless gets saturated, and it can, and does, take an hour
before the last pupil is logged in and ready to work.
Primary school lessons are typically 25 minutes.
Now I can see a way in the long term to reduce that. The wpkg script
will copy the msi to a location on the hard drive, then run the
msiexec command referencing the copy. No improvement this time round,
but when it comes time to uninstall, it doesn't need to copy the msi
again. That should give a factor two improvement. It will also help in
deploying patch versions. To deploy 10.1.2 you deploy the 10.1.0 msi
accompanied by the 10.1.2 msp. Combined, 65M. However the msi for
10.1.0 would already be on the computer.
It also avoids the problem I've got at the moment. I deleted the Adobe
reader 9.4.0 msi, then discovered some computers needed it for the
uninstall when I deployed 10.1.2. (I don't know why they didn't get
10.0.0, 10.1.0 etc...) This means that I now cannot deploy 10.1.2 to
those computers, because the uninstall part of the process fails.
Setting the flag in 10.1.2 not to uninstall doesn't help, because it
simply refuses to install as another version is present.
I had to deploy Number Shark 4 last week. The msi is 450MB. Using
wired connections it took around 15 minutes. Those using wireless,
only 4 at a time, took almost an hour. Fortunately that school only
has 30 laptops, so I managed to finish in a day. I had to pre-arrange
that there would be no laptops available for the whole day though.
i have been hoping I could use wpkg, running as a service, to allow
deployment during lessons. Using AD deployment simply prevents the
lesson from starting. (I only have one day every 3 weeks in each
school, so doing it out of normal hours is generally not possible.)
However the issues described above are making me think it still isn't
going to work.
I appreciate your in-depth reply. It has brought up a lot a valid and
helpful points. We are dealing, currently, with 4 laptop carts each
containing 24 laptops. We have longer class periods (90 minutes). Just
to deploy Firefox (10MB) to a set of laptops would take 45 seconds
assuming ideal conditions (54Mbps). We have Wireless N access points,
but realistically we likely wouldn't come close to that with all 24
clients connected.
From boot to login, it takes about 2-3 minutes. To add much more time
to the login process would be frowned upon. Maybe, the best solution in
this case would be to manually run wpkg from each machine to fetch new
updates/software. Alternatively, I might be able to create an AD user
that has a login script to call wscript. This way I could give said
username to a few staff to help with this process.
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