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First, for anyone who hasn't heard something about the "VCL office hours", 
there is a conference call scheduled every other Tuesday afternoon (4-5pm EST) 
organized and hosted by Andy Rindos from IBM.  This call is not officially 
connected with the Apache Software Foundation.  Andy has been kind enough to 
host the call for various people interested in using VCL and sharing 
information about their experiences via a voice conference call.

Art,

I'm pretty sure I know what is happening with your system.  Hopefully, I can 
communicate it clearly.

VCL keeps any unused machines in a "hot standby" state.  That means it deploys 
the unused machines with some image up until the point of needing to add a 
user account.  It uses a predictive algorithm to select what image to load on 
a machine at the end of each reservation.  The idea is to get through most of 
the deploy procedure before someone requests the image so they only have to 
wait for a small portion of it (adding the user account and setting up access 
rules) when they actually make a reservation.  Any time you see an estimated 
load time of less than one minute, you are hitting a hot standby machine.  If 
there are no machines that have been pre-deployed with the image, you get a 
longer estimated load time, in which case the estimated load time is an 
average of the last several times the image was deployed.

So, at the end of every reservation, an image gets deployed to the machine 
that was used.

The last time we talked about the the GSU setup, you were using the ESX 
deployment module and had a storage array that was somewhat slow.  I haven't 
heard anything about that being changed.  The ESX deployment module makes a 
full copy of the image disk files for every deploy.  So, when you are ending 
your reservation, you are triggering a new deploy on the machine you used, 
which includes a full copy of the disk files on your slow storage array.  If 
you go ahead and make a new reservation before that deploy finishes, you are 
now doing a second full copy of the disk files on your slow storage array, 
which is competing with the first one, making both copies take longer.  If you 
wait the 5 or so minutes you referred to, then you don't slow down the deploy 
time by introducing a second deploy to compete with it.

This problem should go away when you switch to using the VMware deployment 
module that doesn't do full copies at every deploy (it uses VMware's non-
persistent mode when it can) and also when you get a faster storage array.

I hope that clears things up.  Let me know if you'd like me to clarify any of 
it.

Josh

On Thursday June 02, 2011, Art Vandenberg wrote:
>  From the VLC office hours on Tuesday past, I promised to follow up on
> problem I experienced with New Reservation when I'd ENDed a prior
> reservation.
> 
> DISCLAIMER - this was my experience here at GSU, your experience may
> be different.
> 
> SCENARIO 1:
> a) My VCL Matlab session comes to 10 minute warning.
> b) I stop Matlab, logged off, and then END Current reservation (which
> still has not reached end time). NOTE: assume I can not extend past
> our limit.
> c) I immediately request NEW (NOW) reservation; message indicates
> "Estimated Load Time < 7 minutes."
> d) I back off and wait 2 minutes; retry NEW reservation, still
> "Estimated Load Time  < 7 minutes..."
> e) I back off for 5 minutes and when I select NOW reservation, the
> create time shows "Estimated Load Time < 1 minute..." and reservation
> made in < 1!
> 
> SCENARIO 2:
> I subsequently tested same scenario, but this time with a reservation
> that was ENDed but still had nearly 55 minutes remaining... and same
> result:  if I wait 5+ minutes, the "Estimated Load Time < 1"  (and the
> message appears to switch to "< 7 minutes" right at the 5 minute mark
> after ENDing a CURRENT reservation.)
> 
> SCENARIO 3:
> And I then tested what happens if I just go ahead and immediately
> request the NOW reservation (after ENDing a CURRENT reservation) and
> ignore the "Estimated Load Time  < 7 minutes...".  The Pending window
> was open so I could see progress as shown following:
> 
> PENDING WINDOW SNAPSHOT AT 8:08
> State Est/Act
> Time Total
> Time
> confirming image exists(22) 0:04/0:07 0:07
> starting load process(40) 0:06/8:01 8:08
> transferring image files to host server(27) 4:15
> creating configuration file(28) 0:02
> starting virtual machine(48) 0:03
> machine booting(46) 1:08
> running post configuration(9) 0:44
> resource ready(43) 0:00
> adding user account(41) 0:18
> ready for Connect(18) 0:00
> 
> PENDING WINDOW SNAPSHOT AT 8:23
> State Est/Act
> Time Total
> Time
> confirming image exists(22) 0:04/0:07 0:07
> running post configuration(9) 0:50/8:16 8:23
> resource ready(43) 0:00/0:26 8:49
> adding user account(41) 0:18
> ready for Connect(18) 0:00
> 
> PENDING WINDOW SNAPSHOT AT 9:09
> State Est/Act
> Time Total
> Time
> confirming image exists(22) 0:04/0:07 0:07
> running post configuration(9) 0:50/8:16 8:23
> resource ready(43) 0:00/0:45 9:08
> adding user account(41) 0:18/0:01 9:09
> ready for Connect(18) 0:00
> 
> 
> PENDING WINDOW SNAPSHOT AT 9:12
> State Est/Act
> Time Total
> Time
> confirming image exists(22) 0:04/0:07 0:07
> running post configuration(9) 0:55/8:16 8:23
> resource ready(43) 0:00/0:45 9:08
> ready for Connect(18) 0:00/0:04 9:12
> 
> 
> As you see, the "starting load process" took 8:08 minutes to complete
> and image was ready only at 9:12.
> 
> 
> Basically, if I END a reservation before its END time, I should wait
> 5 minutes before requesting NEW reservation.
> ---> I don't need MATLAB to see that (wait 5 minutes + less than 1
> minute for NEW image) IS LESS THAN (don't wait + 9:12 minutes)!
> 
> Whether that argues for a forced wait time in the code (if user has
> ENDed reservation, enforce 5 minute wait before allowing NEW request),
> I leave to others.
> 
> NOTE: Kelly R. advise if you've maybe already adjusted code here at GSU!
> 
> 
> Later
> 
> 
> 
> Art
> 
> Art Vandenberg
> Account Manager/Research Function
> Customer Relations, IS&T
> Information Systems & Technology
> Georgia State University
> avandenb...@gsu.edu
> +1 404 413 4743
> MS Information & Computer Science, Georgia Tech
> MVA Painting & Drawing, Georgia State
> Web page: http://www.gsu.edu/ist/acs/25735.html
- -- 
- -------------------------------
Josh Thompson
VCL Developer
North Carolina State University

my GPG/PGP key can be found at pgp.mit.edu
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