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Wolfgang Friebel, 16.11.2001 C5 report

HEPiX Fall 2001 Report (2) NERSC, Berkeley. Wolfgang Friebel, 16.11.2001 C5 report. Further topics covered. Batch (Sun Grid Engine Enterprise Edition) Distributed Filesystems (Benchmarks) Security (again) (the concept at NERSC). Batch systems.

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Wolfgang Friebel, 16.11.2001 C5 report

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  1. HEPiX Fall 2001 Report (2)NERSC, Berkeley Wolfgang Friebel, 16.11.2001 C5 report

  2. Further topics covered • Batch (Sun Grid Engine Enterprise Edition) • Distributed Filesystems (Benchmarks) • Security (again) (the concept at NERSC) C5 Report

  3. Batch systems • Two talks on SGEEE (formerly known as Global Resource Director – GRD or Codine), see below • FNAL presented new version of their batch system • Main scope is resource management not load balancing • FBSNG, written primarily in Python, Python API exists • Comes with Kerberos 5 support • NERSC reported experiences with LSF • Not very pleased with LSF, will also evaluate alternatives C5 Report

  4. SGEEE Batch • Ease of installation from source • Access to source code • Chance of integration into a monitoring system • API for C and Perl • Excellent load balancing mechanisms (4 scheduler policies) • Managing the requests of concurrent groups • Mechanisms for recovery from machine crashes • Fallback solutions for dying daemons • Weakest point is AFS integration and Token prolongation mechanism (basically the same code as for Loadleveler and for older LSF versions) C5 Report

  5. SGEEE Batch • SGEEE has all ingredients to build a company wide batch infrastructure • Allocation of resources according to policies ranging from departmental policies to individual user policies • Dynamic adjustment of priorities for running jobs to meet policies • Supports interactive jobs, array jobs, parallel jobs • Can be used with Kerberos (4 and 5) and AFS, • Globus integration underway • SGEEE is open source maintained by Sun • Getting deeper knowledge by studying the code • Can enhance the code (examples: more schedulers, tighter AFS integration, monitoring only daemons) • Code is centrally maintained by a core developer team • Could play a more important role in HEP (component of a grid environment, open industry grade batch system as recommended solution within HEPiX?) C5 Report

  6. Scheduling policies • Within SGEEE tickets are used to distribute the workload • User based functional policy • Tickets are assigned to projects, users and jobs. More tickets mean higher priority and faster execution (if concurrent jobs are running on a CPU) • Share based policy • Certain fractions of the system resources (shares) can be assigned to projects and users. • Projects and users receive that shares during a configurable moving time window (e.g. CPU usage for a month based on usage during the past month) • Deadline policy • By redistributing tickets the system can assign jobs an increasing weight to meet a certain deadline. Can be used by authorized users only • Override policy • Sysadmins can give additional tickets to jobs, users or projects to temporarily adjust their relative importance. C5 Report

  7. Distributed Filesystems • Candidates for benchmarking • NFS versions 2 and 3 • GFS (University of Minnesota/Sistina Software) • AFS • GPFS (IBM cluster file system, being ported to Linux) • PVFS – Parallel Virtual Filesystem • Not taken • GPFS – IBM could get it working at NERSC under Linux (not ready?) • PVFS – unstable in tests, single point of failure (metadata server) • AFS – slower than NFS, tests done elsewhere, successfully running • GFS – designed for SAN, runs over TCP with significant performance penalties, lock management not mature, stability for high number of clients not expected to be good. Good candidate for SAN’s C5 Report

  8. Distributed Filesystems • Conclusion for NERSC: only NFS remains, AFS too heavy for them • The talk discussed various combinations of Linux kernel versions (2.2.x and 2.4.x), NFS clients (v2 and v3) and servers (v2 and v3) • Benchmarking tools used • Bonnie • Iozone • Postmark • Benchmarked equipment • Dual 866Mhz PIII with 512MB RAM • Escalade 6200 series 4 channel IDE RAID, with 3 72GB drives striped • Results • By carefully choosing Kernel and NFS Versions throughput can be increased • For much more details consult the talk • Other sites reported very bad NFS performance (confirms NERSC findings, that tuning for NFS is a must) C5 Report

  9. Distributed Filesystems: GFS • Caspur is looking for a filesystem attached to a multinode Linux farm • Looked for SAN based solutions • NFS and GPFS discarded (NFS: performance, GPFS: extra HW & SW) • Have chosen GFS, but trying to use GFS over IP (see next slide) • By using a SCSI to IP converter (Axis from Dothill) they would be able to setup a serverless GFS • Contradicting kernel requirements for GFS and AXIS currently • Issues probably solved (11/2001) with equipment from Cisco • Looks promising to them, more investigations to come C5 Report

  10. C5 Report

  11. Computer Security at NERSC • Very open community, need a balance between security and availability • Main concepts used • Intrusion detection using BRO (in house development, open source) • Immediate actions against attackers (“shunning”) • Scanning systems for vulnerabilities • Keeping systems/software up to date • Firewall for critical assets only(operation consoles, development systems) • Virus wall for incoming emails • Top level staff in computer security and networking • Observed ever increasing scans (30-40 a day!!), threats • Were able to track down hackers and reconstruct the attacks C5 Report

  12. Computer Security: BRO • Passively monitors network • Carefully designed to avoid packet drops at high speeds 622Mbps (OC-12) • Two main components • Event engine, converts network traffic into events (compression) • Policy script interpreter (interprets output of event handlers) • BRO interacts with the border router to drop hosts immediately (using ACL’s) on attacks • BRO records all input in interactive sessions • Allows to reconstruct data even if type ahead or completion mechanisms used C5 Report

  13. Computer Security: BRO • Some of the analysis done in real time, deeper analysis done once a day offline • NERSC is relying heavily on intrusion detection by BRO • NERSC was able to quickly react on the “Code Red” worm (changes to BRO) • Subsequently “Nimda” did very little damage • Many more useful tips on practical security (have a look to the talk) C5 Report

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