We're all in this together: SCD goes to bat for NCAR users

In a high-tech era, human service still counts . . . . . .

Mounting a
tape

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by Lynda Lester
It's 3 p.m. and you've got a model to run at NCAR on the Cray J90.
You submit the job; you wait; you wonder: What's happening on the other end? What's going on, down in the NCAR Computer Room, between the time you start your run and receive your output?
If your job needs data from one of the 178,000 tape cartridges in the offline Mass Storage System (MSS) archives, an SCD operator is on the move -- jogging through a maze of aisles to find the cartridge, grabbing it, and sprinting back to the MSS tape drive to mount it -- then reversing the process to return the cartridge to storage.
It's a big place, the MSS data archives -- a 3,000-square-foot area housing fifty-two rows of eight-foot-tall tape racks. Attached to the front of the tape racks are "sliders" -- additional tape racks that can be moved back and forth when searching for cartridges. In the NCAR Computer Room where space is limited, the sliders increase data storage density by maximizing storage space per square foot.
When an "order" comes in -- One MSS archives file, chop chop!! -- the SCD operator may have to move a couple of sliders -- each holding 800 cartridges and weighing more than 600 pounds when fully loaded -- to get that file. And although the sliders glide smoothly on their tracks, it still takes muscle to heft them back and forth. It also takes time.
And sometimes, when a big job requiring a massive number of cartridge mounts comes in unexpectedly, the MSS wait time on jobs for all users may increase.

A big job
Back in December, a very big job came in. Grant Branstator and Andy Mai of NCAR's Climate and Global Dynamics (CGD) division gave SCD a "heads up" notice: a project they were working on could require up to 11,000 tape mounts. They were studying the seasonality of interannual variability using the Community Climate Model 3 (CCM3), and needed to use a collection of data files netting 1,450 simulated years.
Using this information along with historical records of average mount times, SCD's Computer Production Group (CPG) estimated how long the project would take and how much staff power would be needed -- and adjusted schedules to meet the challenge. During a period of eight days, they mounted 100 cartridges per hour (nearly double the normal amount) -- about half of which were for the CGD project.
In the end, during that "eight-day week," SCD mounted 19,000 cartridges; 10,627 of those mounts were on the SGI Power Challenge XL (winterpark) for the CCM3 Interannual Variability Study.
"The information provided by Grant and Andy helped us reduce the tape-mount wait time for all users," says Bo Connell, head of CPG. "We'd like to thank them for their assistance in making the entire process more efficient for everyone."

Win/win
If you know your project will require a large number of MSS mounts, letting CPG know in advance can help them put temporary measures in place to increase efficiency and reduce wait time, as they did for the CCM3 project.
"That's our goal -- to help everybody," says Bo. "That's what we're here for; that's why we exist. If the users weren't there, we wouldn't be needed."
Which is to say, in a high-tech era, human service still counts. SCD will go to bat for NCAR users -- and there are real people named Katrina, Ingmar, Jeff, John, Melissa, Andy, Julie, and Susan finding files for you down in the NCAR Computer Room.

Contact information
For more information on CPG, see their web page. To contact the CPG, send email to opns@ucar.edu or call 303-497-1200.

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