Tier1 Operations Report 2016-10-19

From GridPP Wiki
Jump to: navigation, search

RAL Tier1 Operations Report for 19th October 2016

Review of Issues during the fortnight 5th to 19th October 2016.
  • There have been some problems over the last fortnight with load on AtlasScratch in Castor. (This did not affect other areas in Castor). The number of Atlas Pilot jobs has been reduced, and then increased, at various times to limit the load on Castor. The weighting of gridftp jobs on atlasScratchDisk within Castor was changed on 10th Oct to increase the job capacity.
  • There have also been load problems on the Castor GEN instance. These have been caused by a large number of accesses from jobs running at other sites by a particular ILC user. This has affected other VOs access to Castor (for example ALICE). We are in contact with the user to tackle this.
  • There was a problem with the squids on Friday (14th Oct). The problem was in the Atlas Frontier system. However, as the squids are multiple-use this had a knock-on effect on CVMFS clients on the batch worker nodes.
Resolved Disk Server Issues
  • GDSS677 (CMSTape - D0T1) failed on Thursday afternoon, 29th Sep. There are no files awaiting migration to tape on the server. It was returned to service on the 6th October. Four disk drives showed various levels of problems and were replaced.
  • GDSS744 (AtlasDataDisk - D1T0) failed in the early hours of Wed. 12th October. After a disk failure the RAID array started a rebuild automatically, bur the disk it was rebuilding on failed just before a complete rebuild. Put back read-only later that day while the rebuild took place on another disk.
  • GDSS612 (AtlasScratchDisk - D1T0) was taken out of production for an hour or so on the 12th October for a battery replacement.
  • GDSS730 (CMSDisk - D1T0) reported reported problems on the 13th October. The RAID card automatically rebuilt onto a drive that itself showed errors. That was then swapped and we rebuilt onto another good drive. Returned to service on the 17th Oct.
  • GDSS658 (AtlasScratchDisk - D1T0) reported FSProbe errors on the 14th Oct and was taken out of service. A battery failure was found. Returned to prod initially read-only later that day. Put back read/write on 18/10.
  • GDSS723 (AtlasDataDisk - D1T0) crashed on Saturday (15th Oct). The cause was not understood. It was put back in service read-only the next day (Sun 16th). The server was taken out of production to run memory tests the following day (Mon 17th). It passed the tests and went back to full production on the next day (Tue 18th).
Current operational status and issues
  • There is a problem seen by LHCb of a low but persistent rate of failure when copying the results of batch jobs to Castor. There is also a further problem that sometimes occurs when these (failed) writes are attempted to storage at other sites.
  • The intermittent, low-level, load-related packet loss that has been seen over external connections is still being tracked. The replacement of the UKLight router appears to have reduced this - but we are allowing more time to pass before drawing any conclusions.
Ongoing Disk Server Issues
  • GDSS648 (LHCbUser - D1T0) failed on Saturday evening (15th Oct). It is showing both disk and network problems. It is still under investigation.
Notable Changes made since the last meeting.
  • On Wednesday 5th October the UKLight Router was replaced. This has also enabled a a 40 GBit connection to the RAL border routers (i.e. giving a datapath of up to 40Gbit for the bypass connection.) We have seen a significant increase in traffic over the bypass route since this change - well exceeding the previous 10Gbit limit.
  • Some re-balancing of the disk servers in lhcbDst has been carried out following a problem where some became full.
  • Some changes were made to increase the number of CMS batch jobs that we run in order to bring the number more into line with the pledge. This was both an increase in the number of worker nodes draining at any time (from 10 to 20) to allow more multi-core jobs (CMS' jobs are purely multicore) as well as an increase in the limit in Condor.
Declared in the GOC DB
Service Scheduled? Outage/At Risk Start End Duration Reason
All Castor Endpoints that Use Tape SCHEDULED WARNING 01/11/2016 07:00 01/11/2016 16:00 9 hours Tape Library not available during work on the mechanics. Tape access for read will stop. Writes will be buffered on disk and flushed to tape after the work has completed.
Advanced warning for other interventions
The following items are being discussed and are still to be formally scheduled and announced.

Listing by category:

  • Castor:
    • Update to Castor version 2.1.15. Planning to roll out January 2017. (Proposed dates: 10th Jan: Nameserver; 17th Jan: First stager (LHCb); 24th Jan: Stager (Atlas); 26th Jan: Stager (GEN); 31st Jan: Final stager (CMS)).
    • Update SRMs to new version, including updating to SL6. This will be done after the Castor 2.1.15 update.
    • Migration of LHCb data from T10KC to T10KD tapes. The additional 'D' tape drives ave been delivered. We await installation into the tape library by the vendor.
  • Fabric
    • Firmware updates on older disk servers.
Entries in GOC DB starting since the last report.
Service Scheduled? Outage/At Risk Start End Duration Reason
Castor GEN instance (srm-alice, srm-biomed, srm-dteam, srm-hone, srm-ilc, srm-mice, srm-minos, srm-na62, srm-pheno, srm-snoplus, srm-superb, srm-t2k) UNSCHEDULED WARNING 12/10/2016 15:00 12/10/2016 16:00 1 hour At risk on some Castor instances while we replace a disk in a headnode.
All Castor storage SCHEDULED WARNING 05/10/2016 09:00 05/10/2016 15:00 6 hours Series of breaks in the external data path to/from our storage while the network router is replaced and tests carried out on the resilience of the links. Internal access to storage unaffected.
Open GGUS Tickets (Snapshot during morning of meeting)
GGUS ID Level Urgency State Creation Last Update VO Subject
124188 Green Less Urgent In Progress 2016-10-03 2016-10-03 Atlas UK Lpad-RAL-LCG224 : Frontier squid down
123504 Yellow Less Urgent Waiting for Reply 2016-08-19 2016-09-20 T2K proxy expiration
122827 Green Less Urgent Waiting for Reply 2016-07-12 2016-09-14 SNO+ Disk area at RAL
121687 Red Less Urgent On Hold 2016-05-20 2016-09-30 packet loss problems seen on RAL-LCG perfsonar
120350 Yellow Less Urgent On Hold 2016-03-22 2016-08-09 LSST Enable LSST at RAL
117683 Amber Less Urgent On Hold 2015-11-18 2016-04-05 CASTOR at RAL not publishing GLUE 2 (Updated. There are ongoing discussions with GLUE & WLCG)
Availability Report

Key: Atlas HC = Atlas HammerCloud (Queue ANALY_RAL_SL6, Template 729); CMS HC = CMS HammerCloud

Day OPS Alice Atlas CMS LHCb Atlas HC CMS HC Comment
05/10/16 100 100 100 96 100 N/A 100 Two SRM tests failed during the network intervention to replace the UKLight router.
06/10/16 100 100 100 100 100 N/A 100
07/10/16 100 100 100 100 100 N/A N/A
08/10/16 100 100 100 100 100 N/A N/A
09/10/16 100 100 93 100 100 N/A 100 A few SRM test failures. Although the tests run against AtlasDataDisk they were coincident with severe problems for AtlasScratch.
10/10/16 100 100 100 100 100 N/A 100
11/10/16 100 100 100 98 100 N/A 100 Single SRM test failure because of a user timeout error
12/10/16 100 100 100 100 100 N/A 100
13/10/16 100 100 100 100 100 N/A N/A
14/10/16 100 100 100 100 100 N/A 100
15/10/16 100 100 100 100 100 N/A N/A
16/10/16 100 100 100 98 100 N/A 93 Single SRM test failure on GET because of a user timeout error
17/10/16 100 100 100 100 96 N/A 97 SRM Test failure on list ([SRM_INVALID_PATH] No such file or directory)
18/10/16 100 91 100 100 100 N/A N/A Some failures of the ALICE AliEn-SE Test. We were aware of problems on the Castor GEN instance caused by heavy use by a user from another VO.
Retrieved from "https://www.gridpp.ac.uk/w/index.php?title=Tier1_Operations_Report_2016-10-19&oldid=12614"