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New tape server software Status and plans

New tape server software Status and plans. CASTOR face-to-face workshop 9-10 December 2013 Eric Cano on behalf of CERN IT-DSS group. What’s being done?. Finish of the push to replace legacy tape software Started with creation of tape gateway and bridge Consolidation into a single daemon

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New tape server software Status and plans

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  1. New tape server softwareStatus and plans CASTOR face-to-face workshop 9-10 December 2013 Eric Cano on behalf of CERN IT-DSS group

  2. What’s being done? • Finish of the push to replace legacy tape software • Started with creation of tape gateway and bridge • Consolidation into a single daemon • Merge stack of bridge, rtcpd, taped (and children processes) • Drop abandoned features: • Leftovers interfaces from Shift/Castor1 • Fortran format translation • Multi-tape files • User file concatenation • Full C++, maintainable software • Interfaces will remain the same (w/exception) • Drop-in replacement, interfacing to gateway, VDQM, VMGR, and SCSI • Logs will use the same interfaces as the stager daemon • Will keep one process per tape mount by forking • Option to kill a session for operators • There will be only one daemon instead of the current stack • This will imply changes on the management & monitoring

  3. What is achieved? • Tape SCSI (st driver + generic SCSI) • Access to tape drives has been reverse engineered • All accesses now make up the interface of “drive” objects, gathered in a single place • All in readable C++ structures, matching the SCSI specs • Simpler device access for generic SCSI ioctl • File structures (AUL format) • Structures have been defined, API not fully defined yet • The threading model has been completely revisited and a proof of concept has been validated • Used to have worker thread running onto a single linked list • Now fully FIFOs based “pipelined architecture”. Each stage has its own FIFO on input. Easy to chop the work into simple steps • All unit tested • Still to be integrated on the master branch • Cmake build (brought to master branch) • Documentation consolidated in a single document (tape server handbook), and completed in parallel

  4. What remains to be done? • Unit testing not yet brought into Castor main branch • SCSI and AUL support still to be merged into Castor master branch • Threading model prototype to be made prod level (error handling, unit testing, etc…) • Session forking has to be tested • VDQM replier to be ported from tape bridge • Link with client libraries for the rest (VMGR, VDQM, tape gateway) • Still a lot to be done, but big subjects have been covered

  5. Going further (post-release 1) • This new tape server software will allow much easier and predictable maintenance • Some idea already floating for follow-up version: • Performance monitoring (on which FIFOs are we waiting?) • Usage of data integrity features of the drives

  6. Timeline • Development started last summer • Targeting delivery for end H1 ’14 • First release will be double release • Like tape gateway • Early testing welcome (to assess impact of changes on other sites)

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