1 Data Storage MICE DAQ Workshop 10 th February 2006 Malcolm Ellis & Paul Kyberd.
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1 Data Storage MICE DAQ Workshop 10 th February 2006 Malcolm Ellis & Paul Kyberd
2 Introduction During January Paul and I had a meeting at Brunel to make a first stab at estimates for data storage and transfer requirements for MICE. Based on some rough estimates (hopefully biased towards the worst case) of data size and rate and aim to develop a plan to securely maintain all the data that is taken as well as distribute it throughout the collaboration for processing and analysis. Most of this talk consists of slides that were presented by Paul at a MICE-UK meeting recently.
3 Data Flow in MICE Mice Hall Fermilab Tier-1CERN Tier-1KEK/Osaka Tier-1 Atlas Tier-0
5 Data rate from Detectors Tracker can conceivably operate in several data taking modes: –Discriminators only: allows higher trigger rate, but results in lowest event size and data rate. –Discriminators and ADC/TDC information: required for calibration and in the event of high RF background rate. Will probably result in a lower trigger rate being achieved, but due to much larger event size will produce the largest data rate. First estimate of PID detectors indicates that tracker produces the bulk of the data (when it writes out ADCs and TDCs)
6 Data Rate from the detector Estimate: Tracker data Rate if full data readout is required for the tracker 14 MBytes/s (110 MBits/s) – all other data negligible Data per hour50 GigaBytes Data per day1 TeraByte ISIS efficiency ~75% over an extended period Running schedule: unknown – assume the LHC 4 months. Data per year120 TeraBytes Data for MICE<0.5 PetaBytes
7 Data Rate from Monte Carlo Unknown: Assume Monte Carlo totals are the same as data. Data per year120 TeraBytes Data for MICE<0.5 PetaBytes Plan to use Monte Carlo pre-startup to test data flow rates
8 Hardware requirements for the hall Local storage needed to buffer data before dispatch to Atlas and to allow running when link or centre is unavailabledata deleted when TWO copies exist. Data per day1 TeraByte Weekend running – Friday to Monday ~ 3 TeraBytes Disk server with 10 eide drives – each 500 GigaBytes. 2*5 RAID-5 arrays – striped across all 10 disks 8 TeraBytes By the time is comes to purchase the disks,larger capacity disks will be available
9 Hardware for link to Tier-0 Tracker data Rate if full data readout is required for the tracker 14 MBytes/s (110 MBits/s) Peak must allow reverse traffic for remote operation of detector subsystems. Transferring data delayed by unavailability of Atlas storage. Gigabyte link – gives approximately a factor 4 in safety (at 40% collisions become a problem).
10 Hardware at Tier-0 Data per year120 TeraBytes Data for MICE<0.5 PetaBytes 400 TeraBytes tape for data – none for Monte Carlo. 120+30 TeraBytes of disk space ( MC is divided between the four centres ) Ability to write tape data at 110 Mbytes/s ( see data security ) *2 for monte- carlo
11 Hardware links from Tier-0 Tracker data Rate if full data readout is required for the tracker 14 MBytes/s (110 MBits/s) Ability to copy the data to one remote site in real time 110 MBits per second off-site average rate Higher unless two tier-1 sites can read 110 Mbits per second and relay at the same rate.
12 Hardware at Tier-1 Data per year120 TeraBytes Data for MICE<0.5 PetaBytes 120+30 TeraBytes of disk space ( Fast storage ) 400 TeraBytes near-line storage Ability to receive data at 110 MBits/s and for two of them to relay at this rate.
13 Note on tier-1 data links CERN can clearly handle the traffic. FermiLab can handle the traffic. Japan may be a problem. if so transfer selectively processed data. Not established if they will
14 Note on data security MICE data will consider to be safe when there are two distinct copies. During the writing of a single file in the hall only 1 copy. Writing to Tier-0 create a second copy. Deletion of the hall copy is allowed when an extra external copy has been created. In normal running this will be copy to a tier-1 centre. ( The first copy will be rotated between tier-1s ) If this is not possible we will create immediate tape copies at the tier-0. ( alternative external sites are not considered to be helpful ) Bookkeeping decisions will influence data taking rules
15 Data Flow in MICE Mice Hall 4 TeraByte disk 1 GigaBit Link 400 TB Fermilab Tier-1 110 MegaBit Link 150TB fast storage 400TB slow storage CERN Tier-1 110 MegaBit Link 150TB fast storage 400TB slow storage KEK/Osaka Tier-1 110 MegaBit Link 150TB fast storage 400TB slow storage 110 MegaBit relay Two copies of data required at all times 150 TB Atlas Tier-0 1 GigaBit Link
16 Data Processing Plan to use LCG for both Monte Carlo production and real data analysis. Have made a slow start, GRID hardware installed in the UK for MICE (Sheffield and Brunel) and a VO has been created. Post-Osaka, plan to ramp up GRID activities through G4MICE simulation studies. Larger productions and transfers of large volumes of Monte Carlo can be used to test data-taking systems.
17 Local Processing Some sort of farm will be required on the floor (or at least on the RAL site) in order to provide feedback for beam tuning and for online monitoring. An estimate from Tom Roberts is that during beamline tuning runs of approximately 10k events in a minute will be collected and will need to be reconstructed (to determine Twiss parameters). This reconstruction will need to be performed on a comparable time scale to allow quick feedback to the beamline settings.
18 Next Steps Need to become more definite about event sizes, trigger rates and running periods to confirm estimate of total data storage and transfer rate requirements. Reconstruction will need to be tested (once at a sufficient level for online work) to estimate online processing needs. Paul has already started on a list of networking/storage requirements for the RAL site. Need to establish local contacts at FNAL, CERN and Japan for Tier-2 centres. Alan has started process of arranging computing resources at FNAL for MICE.