PandaDynamicDataPlacement

Introduction

This page describes PanDA Dynamic Data Placement (PD2P).

General Policies

The following general policies apply to PD2P algorithm for making replicas of datasets at Tier 1 and Tier 2 sites.
  • The dataset name prefix is mc or data
  • The data type is not RAW,RDO,HITS,ESD,EVNT
  • The hidden metadata is not True
  • Destination of all PD2P datasets will be DATADISK
  • Dataset replicas on LOCALGROUPDISK are ignored
  • Skip GangaRobot, HammerCloud, _dis, _sub etc
  • Site must have sufficient free space. The total disk size and disk usage are obtained using DQ2.queryStorageUsage(). The threshold is max(totalDiskSize*5%,3TB).
  • Site must be analysis, not test, production etc
  • Replicas at non-online sites are ignored
  • Only online sites are used

Tier 1 Algorithm

It is specified as SELECTEDT1 in PD2P log.
  • Primary copies of ATLAS data will be placed at Tier 1 sites based on CREM policies
  • PD2P will make additional copy at Tier 1 if:
    • no PD2P replica was made during the past week to a T1
    • int(log10(nused))>nSecondaryT1Replicas, where nused stands for how many times the dataset was used per jobset
    • log10(nused) == 10**int(log10(nused)) (it means that another replica is created when nused=10,100,1000,... and not for nused=1)
  • All T1s are used even if no T2 has shcedconfig.cachedSE=True in the cloud
  • Location of additional 'secondary' copy is based strictly on MoU share
  • If dataset is a container, each containing dataset is placed using MoU share
  • immediately makes an additional copy at a Tier 2 using MoU share (SELECTEDT2_T1MOU in PD2P log)

Tier 2 Algorithm

Tier 2 Algorithm is executed independently of Tier 1 Algorithm. If one or more sites in a cloud have shcedconfig.cachedSE=True, the cloud is regarded as a PD2P cloud. When an analysis job is submitted to Panda, PD2P is triggered. Datasets which match the following conditions are distributed.
  • The dataset was used one or more times before the job is submitted. I.e., nUsed>0, where nUsed is how many times the dataset was used beforehand
  • No replica within PD2P T2 sites (nSitesHaveDS=0). Or if nWaitingJobsets>2, the number of replicas should be less than maxSitesHaveDS=int(log10(nWaitingJobs/200)). nWaitingJobsets is the number of Jobsets which have at least one waiting job. nWaitingJobs is the number of waiting jobs. Both nWaitingJobsets and nWaitingJobs are computed per dataset when the analysis job is submitted. The maximum value of maxSitesHaveDS is limited to 5. This condition is checked only for nUsed>1, i.e., the second analysis job always triggers PD2P
  • The number of active DQ2 subscriptions per dataset made by PD2P is not greater than 2
maxSitesHaveDS is checked only for the second and subsequent analysis jobs. PD2P makes a copy at a candidate site with shcedconfig.cachedSE=True from any PD2P cloud by using the weight. The site must have fast FTS channel to sites which already have the replica. In PD2P log, it is specified as SELECTEDT2_JOB for nUsed=1, SELECTEDT2_NOREP for nSitesHaveDS=0, or SELECTEDT2_WAIT for others. Another copy is made t a Tier 2 using MoU share when nUsed=1 (SELECTEDT2_T2MOU in PD2P log).

where

  • W … The same weight for analysis brokerage described in this link
  • S … The number of subscriptions made by PD2P to the site for last 24 hours + 1
  • R … The number of replicas of the dataset in T2 sites in the same cloud + 1

A new copy tends to go to another cloud due to the second negative weight if a T2 site in a cloud already has a copy. If the input is a dataset container, one candidate is found for each constituent dataset.

Logger

PD2P Logger

  • action=UNSELECTEDT2 : Selection according to brokering algorithm
  • action=SELECTEDT2_T2MOU : Selection according to a/b/c/d classification

Monitor

All the monitorings associated to PD2P and extracted from the logger informations are documented in PD2P Monitor

Additional Information


Major updates:
-- TadashiMaeno - 15-Nov-2010 -- Revised KaushikDe - 13-Apr-2011



Responsible: TadashiMaeno

Never reviewed

Topic revision: r27 - 2013-02-21 - TadashiMaeno
 
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