Week of 171030

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Tier-1 downtimes

Experiments may experience problems if two or more of their Tier-1 sites are inaccessible at the same time. Therefore Tier-1 sites should do their best to avoid scheduling a downtime classified as "outage" in a time slot overlapping with an "outage" downtime already declared by another Tier-1 site supporting the same VO(s). The following procedure is recommended:

  1. A Tier-1 should check the downtimes calendar to see if another Tier-1 has already an "outage" downtime in the desired time slot.
  2. If there is a conflict, another time slot should be chosen.
  3. In case stronger constraints cannot allow to choose another time slot, the Tier-1 will point out the existence of the conflict to the SCOD mailing list and at the next WLCG operations call, to discuss it with the representatives of the experiments involved and the other Tier-1.

As an additional precaution, the SCOD will check the downtimes calendar for Tier-1 "outage" downtime conflicts at least once during his/her shift, for the current and the following two weeks; in case a conflict is found, it will be discussed at the next operations call, or offline if at least one relevant experiment or site contact is absent.

Links to Tier-1 downtimes

ALICE ATLAS CMS LHCB
  BNL FNAL  

Monday

Attendance:

  • local: Alberto (monitoring), Cedric (ATLAS), Enrico (storage), Gavin (computing), Jan (storage), Julia (WLCG), Maarten (SCOD + ALICE + GGUS), Marian (networks), Vincent (security), Vladimir (LHCb)
  • remote: Andrew (NLT1), John (RAL), Kyle (OSG), Marcelo (CNAF), Pepe (PIC), Sang-Un (KISTI), Tommaso (CMS), Vincenzo (EGI), Xin (BNL)

Experiments round table:

  • ATLAS reports ( raw view) -
    • Activities:
      • Normal activity
      • Continuously >250k of running slots of jobs
      • Still huge number of jobs to process at the T0
      • We foresee a derivation campaign on data in 2-3 weeks
    • Problems
      • Backlog moving files from EOS to Castor. Being investigated
        • Jan: the matter is being investigated; it does not seem to be on the CASTOR side;
          the GridFTP doors may be overloaded at times, and therefore we recommend
          that Xrootd be used instead for "internal" transfers between CASTOR and EOS
      • Low transfer efficiency between one T2 and Russian T1 : GGUS:131375

  • CMS reports ( raw view) -
    • all resources under heavy use.
    • Tier-0 suffering from backlog. 40k jobs "late" with respect to first possible start. CMS started to overflow to the CERN T2 resources; currently not much more than a test, can ramp up if needed.
    • Tier-0 backlog mostly to KIT; disk + tape O (1 PB). Changed after XeXe run decreased the slope, but did not invert the sign
    • disk storage equally suffering, 3 Tier-1s over 90%: JINR, CNAF, KIT
    • overall "unmovable" disk is climbing fast towards 80% of the total. A disk cleaning will be needed in short notice

  • ALICE -
    • High activity on average
    • CERN: more EOS crashes Fri evening (OTG:0040600).
      • A storm of activity appears to have triggered a bug in XRootD.
      • A mitigation was applied while the matter is not understood.

  • LHCb reports ( raw view) -
    • Activity
      • Monte Carlo simulation, data processing and user analysis
      • pre-staging progressing well
    • Site Issues
      • T0:
        • NTR
      • T1:
        • CNAF Alarm ticket (GGUS:131366) solved
        • Vladimir: there also appears to have been a temporary overload due to staging from tape to disk at RRC-KI

Sites / Services round table:

  • ASGC:
  • BNL: NTR
  • CNAF:
    • Xrootd problem for CMS still under investigation. (GGUS:131385)
    • the issue from the LHCb alarm ticket was caused by a missing firewall rule
  • EGI: NTR
  • FNAL:
  • IN2P3:
  • JINR: Nothing to report
  • KISTI: NTR
  • KIT:
  • NDGF: Oslo will upgrade pools Wed Nov. 1 14-15 CET. Short outages expected during reboot. Some Atlas data affected. (Christian,Can't attend. In another meeting.)
  • NL-T1: NTR
  • NRC-KI:
  • OSG: NTR
  • PIC:
    • on Nov 7 we will have a downtime to upgrade dCache, reboot WN for kernel patches
      and do a firmware update in the tape library
  • RAL: NTR
  • TRIUMF: Apology for that I could not join. For the issue reported in GGUS ticket, 131004, it should be caused by that the tape writing pools were getting full, thus there were not enough available slots for data transferred to tape. Our storage expert did some changes to mitigate this problem last Monday, this situation should be improved.

  • CERN computing services:
    • SIR for LHCb VO box incident: ServiceIncidentCloud20171017. TL;DR possible hot-spot, being investigated.
    • Have noted no ill effects from last week's CREAM retirement.
  • CERN storage services: NTA
  • CERN databases:
  • GGUS: NTR
  • Monitoring:
    • NTR
  • MW Officer:
  • Networks:
    • GGUS:128489 - RO-02-NIPNE to multiple sites - MTU step-down suspected in combination with some load balancing (MPLS, LAG)
  • Security: EGI SVG Alert: up to critical kernel vulnerability:
    • Only on RHEL7 derivatives, if unprivileged user namespaces are allowed (namespace.unpriv_enable=1 in kernel and user.max_user_namespaces sysctl non zero)
    • Singularity "non-SUID" deployment would be affected

AOB:

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Topic revision: r19 - 2017-10-30 - GavinMcCance
 
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