Data & Storage Services CERN IT Department CH-1211 Genève 23 Switzerland t DSS 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

CERN IT Department CH-1211 Genève 23 Switzerland t Internet Services DSS 2New tape server softwareCastor Workshop Dec 2013 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

CERN IT Department CH-1211 Genève 23 Switzerland t Internet Services DSS 3New tape server softwareCastor Workshop Dec 2013 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

CERN IT Department CH-1211 Genève 23 Switzerland t Internet Services DSS 4New tape server softwareCastor Workshop Dec 2013 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

CERN IT Department CH-1211 Genève 23 Switzerland t Internet Services DSS 5New tape server softwareCastor Workshop Dec 2013 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

CERN IT Department CH-1211 Genève 23 Switzerland t Internet Services DSS 6New tape server softwareCastor Workshop Dec 2013 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)