Note: This article was published in Fall 1997. For the latest on GAU charges, see http://www.scd.ucar.edu/docs/charges
On August 1, 1997, SCD instituted a change in the GAU (General Accounting Unit) calculation for community users. SCD did this in order to:
- Simplify the GAU using the CRAY C90 hour as a base instead of the CRAY Y-MP hour
- Recalculate Mass Storage System (MSS) charges to reflect current costs
SCD changed the GAU calculation to reflect the decommissioning of the Y-MP (shavano) and the installation of the C90 (antero). The GAU is now more consistent with
current NCAR computing services. GAU allocations for users are unchanged.
This "new GAU" was approved by the SCD Advisory Panel and
presented to SCD User Group (SCDUG) representatives for discussion and comments.
Simplified formula
Previously, GAU charges for Cray usage were calculated using
a complex, detailed formula involving such factors as CPU time, I/O, memory
and disk usage, MSS access (from the Crays), and so forth.
The new GAU formula is simply based on CPU time, the computer factor (assigned to each computer based on its relative compute power), and the job queue charge factor.
The standardized, more simplified GAU calculation is:
- new_GAU = CPU_time * computer_factor * queue_factor
The computer factors for community resources are:
CRAY J924se (ouray) .25
CRAY J916 (paiute) .25
The computer factor for Climate Simulation Laboratory J9 is:
CRAY J920 (aztec) .25
The new job queue factors are:
Interactive (ia) 2.0
Premium (prem) 1.4
Regular (reg) 1.0
economy (econ) 0.8
Near dedicated (nd) 0.4
Real time (rt) 1.75
Special (spec) 1.0
Queue adjustments
Historically, community users have done most of their computing in the
economy queue with relatively little use of the higher priority queues.
The result has been poor turnaround time for most jobs due to overload of
the economy queue.
In an effort to give users more flexibility in using
the priority of job queues, the new GAU delivers about 20%
more CPU cycles in the regular queue than the old GAU delivered in economy.
Since GAU allocations are unchanged but the compute power per GAU has
increased, users now have the option to do most
of their computing in the regular queue. Users can use the premium queue to expedite turnaround when needed, but at a 40% surcharge.
If users want to
replenish the additional GAUs spent via the premium surcharge, they can use the economy queue for some jobs. For example, two hours spent in the economy
queue will offset the surcharge levied for using one hour in premium.
MSS charge changes
Previously,
MSS charges were generated both
on the Cray host machine and on the MSS machine. MSS
charges on the Cray host machine have now been eliminated; charges on the
MSS machine have been adjusted upward to compensate for this change and
for the growth in MSS usage costs and demands.
(These increases are
approximately a 14% increase for data access, a 57% increase for normal
storage, and a 150% increase for storage on private volumes).
Even though
total allocations to NCAR divisions and to university projects are unchanged, the
new GAU formula on the Cray machines generally allows for this increase in
MSS charging.
Charging document
The
"Charges for SCD Computing Resources" document has been updated to reflect the recalculation of GAU and MSS charges.
Information on all other standard queues is also included. This
document is on the Web at:
http://www.scd.ucar.edu/docs/charges
If you have questions or concerns, please contact the Technical Consulting Office (consult1@ncar.ucar.edu or 303-497-1278).
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