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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