Changes in pd2p replication strategy
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Changes in PD2P replication strategy. S. Campana ( CERN IT/ ES) on behalf of ADC. Current PD2P algorithm. For T1s: distributes proportionally with T1 MoU share This is OK, we do not discuss this today For T2s: same algorithm as job brokering

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Changes in pd2p replication strategy

Changes in PD2P replication strategy

S. Campana(CERN IT/ES)

on behalf of ADC

Current pd2p algorithm
Current PD2P algorithm

  • For T1s: distributes proportionally with T1 MoU share

    • This is OK, we do not discuss this today

  • For T2s: same algorithm as job brokering

    • Send a copy to the place which has higher chance to run a job once the dataset gets there

    • Weight ~ #CPUS * #Running / # Waiting

  • The current algorithm is optimized for re-brokering

    • And offloading the T1

  • Not necessarily it is optimal for an balanced data distribution

    • The main purpose of PD2P is to replicate popular data for reuse

Presentation Title - 2

New pd2p algorithm
New PD2P algorithm

  • PD2P will use two different algorithm for

    • Express replica (for quick reuse)

    • Long Term replica (aimed to balanced data distribution)

  • Express replica

    • Same algorithm as today.

      • Quick data delivery (use ClosedSites only)

      • Possibility to run promptly a job on the new replica

  • Long Term Replica(s)

    • Based on size (disk) of the site

    • Based on performance in Analysis Functional Tests (last month)

Presentation title - 3

Pd2p and pre placement
Pd2P and Pre-Placement

  • PD2P and Pre-Placement of data are (almost) orthogonal

    • PD2P replicates only what has been used – with a minimal delay

    • Pre-Placement replicates everything

      • The delay can be very short but also very long (congestion after reprocessing for example)

  • ADC would prefer to have only one mechanism for Data Replication: PD2P

Presentation title - 4


  • We leave the situation unchanged for T1s and CERN

  • We keep going with no pre-placement for T2s

  • We increase the number of replicas from PD2P create on first use (and subsequent uses):

    • One Express Replica at T2s

    • Two Long Term replicas at T2s

  • PD2P is applied to ADOs, (D)ESDs, NTUP

    • Both Data and MC

    • Including what is produced by Group Production

Presentation title - 5

Monitoring and docs
Monitoring and Docs

  • The PD2P twiki


  • PD2P replication (tables) from Mikhail


  • PD2P logs from Tadashi


  • Plots from Jarka (will be moved soon, check the twiki above)


Presentation title - 6