# Presentation: 324697

## CDF Run II Computing Workshop.A user’s perspective

- Stefano Belforte
- INFN - Trieste

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## “A user of what ?” (Avi Yagil)

- Perspective of a User(s) of data at a remote institution
- Data Analysis in Italy for CDF Run II
- Why ?
- I have to make a plan for computing for the Italian CDF collaborators for Run II:
- what hardware
- where
- when
- how much money

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Which Hardware for data Analysis in Italy ?

- CPU, Disks, Tapes (Robots?), Network (LAN, WAN)
- I am going to share my exercise now with you
- hopefully I learn something from discussion
- maybe I help you focus your questions
- Italy is many institutions, all sizes, one will be like yours
- what is really different ? The WAN maybe.
- But in RunII many transoceanic institutions....

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Bottleneck:  I/O, very difficult to put data into the CPU
solution: bring the CPU to the data, build powerful cluster 

- solution: bring the CPU to the data, build powerful cluster

**Run I vs. Run II**

- Beware these numbers. Very difficult to make good predictions. Hope that conclusions do not change if numbers are a bit wrong.

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Hardware at home. Copy FNAL setup again ? 

- _FERMILAB_
- 500 GBytes  20 TBytes
-  x 40 !
- VMS cluster  high performance Fiber Channel based Storage Area Network
- Hand tapes + Silo  million $ robot

- _PADOVA / PISA_
- 30 GBytes  2 TByte ?
- VMS cluster  Just a Bunch of Unix/linux boxes
- hand tapes  hand tapes ?

- Anyhow, simple scaling doesn’t work. Data can not be parted among physicists.
- Also would like to do better then Run I, more analysis more easily

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## How much data must I handle at home?

- Liz’s Table, see :http://www-cdf.fnal.gov/internal/upgrades/computing/offline_minutes/buckley_vr_talk_jan_99.psPage 5.

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## PAD vs. Ntuple

- Ntuple: 1000 variables/event = 4KByte/ev (PAD = 60 KB)
- High Pt:  O(1% total data) keep all events
- PAD: 2TBytes, 20 tapes        analyze at home
- Ntuple: 200 GBytes            keep on PC hard disk
- but ! Need several versions of the Ntuple, reduce 1/4 at most
- Low Pt:  O(10% total data)
- PAD: 20TB, 200 tapes        have to do something
- Ntuple: 2TB                        don’t fit on disk !
-  Reduce data sample ? 1/10th  Low-Pt = High-Pt
- anyhow is analysis dependent, ,many people... many opinions
- still... how do I bring those data in Italy ? Few tens to few TB..

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Network needs for Analysis(from a talk to INFN in Bologna January 19, 1999)

- 3 Scenarios (extremes and middle way):
- copy all PADs in Italy, need almost no net to US
- leave all PADs & “ntuple” in US, use Xterm from Italy
- copy some PADs here, keep most Ntuples here (copy/create)
- Difficult to estimate requirements. Better the other way around. Given 4 Mbit/sec dedicated to CDF, what can we do ?
- 4	Mb/sec = 200GByte/week = 2 tapes/week, can’t beat DHL !
- 1 tape a day = 100GByte/day = 10 Mbit/sec
**PADs don’t travel on the net**
- 4Mb/sec / 10 users = 1GByte/5hr/person for copying Ntuples
- one analysis = 1/10th data  PAD=20TB, Ntuple=20GB ? refreshing Ntuple takes 4 days min ! More data, more users..
- Converging argument: 10GB ntuple/physicist = minimum !
**Can’t make Ntuple offsite and copy locally on the net**

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## What goes out of  FNAL ?

- PADs don’t travel on the net
- Ntuples don’t travel on the net
- what do I do ?

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## What is an Ntuple anyway?

- Do we really need to refresh ~200 GBytes of Ntuples “continuously” ?
- The Ntuple is what we use for interactive histogramming.
- If it takes one hour to get the histogram, may very well submit a job and get the histograms back.
-  _Data transfer is limited, it makes no difference where the job runs_ !
- An Ntuple is a data-set you go through in a few minutes at most
- disk  CPU: 50 Mbytes/sec at most  3 GBytes/min at most.
- Ntuple will always fit in your desk(lap)top PC !
-  Notice: Run I equivalent (200MByte) required good chunk of 5” big SCSI disk !

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Disk to CPU

- standard desktop PC vs. Powerserver

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Getting Ntuple home

**Easier way:** the WAN. T1 for 2 (500Kbit/sec/user)  0.5GByte/hour(now we deal with CDF notes, a few MBytes, here we go x1000 !)
- 6 hours to get my Ntuple, a day or two more likely... NO WAY !
-  internet future may be brighter, Ntuples may be bigger...
-  _if possible:_ maybe slow, likely unsafe, but easy
**3 alternative solutions:**
- Don’t do it! Run “PAW” at Fnal (just Xterm+telnet). Fast, easy and safe
-  500Kbit/s = 10 good Xterm sessions (or 5 perfect)
- FedEx (1 lb, 5 days a  week)                           easy and safe
-  Fnal -> US 1st(2nd) day 400(200) $/year
-  Fnal -> Europe 7k$/year
- create Ntuple locally from FedEx’ed PADs      safe but **hard**

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Data Analysis in Pisa: The Final Answer(from a talk to INFN in Pisa May 12, 1998)

- We will have to try, can’t pick the right approach before collaboration has finalized data handling and distribution tools, and analysis topics have been pinpointed
- We will try everything, user pressure will drive
- Needs will be dominated by physics output (maybe we find SUSY in 3-lepton samples and everybody looks at this small data set...)
- We will exploit local computing as much as possible to reduce network load (likely bottleneck, as it always has been)
- Still will need to access FNAL PADs to produce data sets to copy to Pisa. If network is no good will use tapes (expensive though!). But we **desperately need guaranteed bandwidth for interactive work**
**If can not log in FNAL, no way to do most analysis here, only use “dead” data sets: no express data, no hot topics, just late sidelines... the good old way: take the plane and go to FNAL.**

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Dealing with PADs at home

- Easily 1~5 TB, what to do ?
- All on disk ? 20 to 100 disks... and no VMS cluster...
- Multi CPU Server+RAID ?
-  Small SUN ? Or Big PC ?
- PC farm (our small Level 3?) ? LAN !
- Tape stacker ? 1~2 TB only? A couple of drive ? So slow !
- Taking shift at tape mounting ? 5 PCs, 10 drives, 50 tapes... but... will beat the robot ?
-  Power server at FCC ?
- Up to 500GB: all on disk. 2 ~ 3 PC’s working together.
-  LAN, LAN, LAN !
- Morale: the less you need it, the better it is.

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Where to put a Power Unix Server with 5 TB disk ?

- See e.g.:http://www-cdf.fnal.gov/upgrades/cdfdh/doc/hardware/hard_arch.psa.k.a. cdfsga:/cdf/pub/cdf4707_r2dh_hard_arch.psFigure 3

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Tapes

- Anyhow will need tapes for more then import to disk
- PADs, simulation, MonteCarlo, ...
- Will need to run analysis jobs from tape, just like at FNAL
- But in Run II all tape data must be spooled to disk first
- spool space: 100 GBytes each (one full tape) ?
- Not likely
- Better spool 10 GBytes a time
- Better be a free parameter

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Summary

- need FedEx
- need to run at FNAL: low latency WAN
- need flexible software at home
- need good LAN at home
- need flexible expandable hardware at home

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## Conclusions

- recommendation to INFN
- recommendations (requests) to managers

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## To my colleagues

- buy “nothing” now
- buy little (few PC’s, few tapes, little disk) next year, add disks as needed (JIT !)
- get the best LAN and WAN you can
- try to do the most at FNAL, ship tapes every day if need be, put CPU and or disks in FCC if needed
- see how it goes, see where the market goes
- be prepared to handle few TB in 2001/2
-  get a computer room ready
-  don’t know which hardware will be best, but likely it will not fit on your desktops

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999

## To the Offline Managers

- tapes, disks & CPU for everybody (lot’s of)
- friendly, low latency batch i/f from home (www ?)
- fast, easy-to-use i/f from Robot to FedEx
- help for simple linux system at home:
- suggested/supported hardware configuration
- easy to use/install software, adaptable to limited hardware setup
- one example on-site OFF the LAN

- Stefano Belforte - INFN Trieste

- Febryary 10, 1999