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Introduction to the NERSC HPCF NERSC User Services. Hardware, Software, & Usage Mass Storage Access & Connectivity. Hardware, part 1. Cray Parallel Vector Processor (PVP) Systems 96 CPUs, Shared-memory parallelism (Cray tasking, OpenMP); - PowerPoint PPT Presentation
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NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
Introduction to the NERSC HPCFNERSC User Services
Hardware, Software, & Usage
Mass Storage
Access & Connectivity
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
2
Hardware, part 1• Cray Parallel Vector Processor (PVP) Systems
– 96 CPUs, Shared-memory parallelism (Cray tasking, OpenMP);
– J90SE clock is 100 MHz; peak performance is 200 Mflops/cpu (~125, actual)
– SV1 clock is 300 MHz; peak performance is 1200 Mflops/cpu (~300, actual)
– J90Se and SV1 are not binary compatible
• Cray T3E MPP System– mcurie
– 692 PEs: 644 application, 33 command, 15 OS; 256 MB/PE
– PE clock is 450 MHz; peak performance is 900 Mflops/PE (~100, actual)
Name Type # CPUs Memory Purpose
killeen J90SE 32 1 GW (8 GB) Interactive, weekdays;
Batch, up to 256 MW, 24x7, subject to
weekday suspension
seymour SV1 16 1 GW (8 GB) Interactive, weekdays;
Batch, up to 256 MW, 24x7, subject to
weekday suspension
bhaskara SV1 24 1 GW (8 GB) Batch, up to 512 MW
franklin SV1 24 1 GW (8 GB) Batch, up to 512 MW
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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Hardware, part 2• IBM SP MPP System
– gseaborg, Phase 1
– 304 nodes (608 CPUs): 256 (512) compute, 8 (16) login, 16 (32) GPFS, 8 (16) network, 16 (32) service); 1 GB/node
– Node clock is 200 MHz; peak performance is 800Mflops per CPU (~200, actual)
– Phase 2 will be bigger and faster
• Visualization Server– escher; SGI Onyx 2
– 8 CPUs, 5 GB RAM, 2 graphic pipes
– CPU clock is 195 MHz; 2 simultaneous video streams
• Math Server– newton; Sun UltraSPARC-II
– 1 CPU, 512 MB RAM
– CPU clock is 248 MHz
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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Hardware, part 3
• Parallel Distributed Systems Facility (PDSF)– High Energy Physics facility for detector simulation and data analysis
– Multiple clustered systems; Intel Linux PCs, Sun Solaris workstations
• Energy Sciences Network (ESNet)– Major component of the Internet; ATM Backbone
– Specializing in information retrieval, infrastructure, and group collaboration
• High Performance Storage System (HPSS)– Multiple libraries, hierarchical disk and tape archive systems
– High speed transfers to NERSC systems
– Accessible from outside NERSC
– Multiple user interface utilities
– Directories for individual users and project groups
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: File Systems, part 1
• $HOME
– “permanent” (but not archival)
– 5 GB quota, regular backups, file migration
– local to killeen, NFS-mounted on seymour and batch systems
– poor performance for batch jobs• /u/repo/u10101• /Un/u10101• /u/ccc/u10101• /U0/u10101
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: File Systems, part 2• $TMPDIR
• temporary (created/destroyed each session)
• no quota (but NQS limits 10 GB - 40 GB)
• no backups, no migration
• local to each machine– high-performance RAID arrays
– system manages this for you
• A.K.A. $BIG
• /tmp• location of $TMPDIR• 14-day lifetime
• A.K.A. /big• you manage this for yourself
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 1
• Unicos• Shells
– Supported• sh• csh• ksh (same as sh)
– Unsupported• tcsh (get it by “module load tcsh”)• bash (get it by “ module load tools”)
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 2• Modules
– Found on many Unix systems
– Sets all or any of environment variables, aliases, executable search paths, man search paths, header file include paths, library load paths
– Exercise care modifying startup files!
• Cray’s PrgEnv is modules-driven
• Provided startup files are critical!– Add to .ext files, don’t clobber originals
– Append to paths, don’t set them, and this only if necessary
– If you mess up, no compilers, etc.
• Useful commands• module list• module avail• module load modfile• module display modfile• module help modfile
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 3• Programming
– Fortran 90 - f90– C/C++ - cc, CC– Assembler - as– Use compiler (f90, cc, CC) for linking also
• f90 file naming conventions– filename.f - fixed form Fortran-77 code– filename.F - fixed form Fortran-77 code, run preprocessor first– filename.f90 - free form Fortran 90 code– filename.F90 - free form Fortran 90 code, run preprocessor first
• Multiprocessing (aka multitasking, multithreading…)– setenv NCPUS 4 (csh)– export NCPUS=4 (ksh)
– "a.out: Command not found.”– ./a.out … (Note: No parallelism specified with execution)
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 4a• Execution modes
– Interactive serial• 10 hours on killeen and seymour
• 80 MW max memory
– Interactive parallel• No guarantee of real-time concurrency
– Batch queues
* = killeen, seymour, franklin, bhaskara ** = franklin, bhaskara• To see them: qstat -b
• Queues shuffled at night, and sometimes during the day
• Subject to change
Queue Memory Limit(MW)
CPU TimeLimit (HRS)per Process
CPU TimeLimit (HRS)per Request
Disk SpaceLimit (GB)
debug_small * 80 0.5 0.5 40
st_80 * 80 120 121 40
st_256 * 256 120 121 40
st_512 ** 512 12 13 40
mt_512 ** 512 120 121 40
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 4b
• Batch– User creates shell script (e.g., “myscript”)– Submits to NQE with “cqsub myscript”
• Returns NQE task id (e.g., “t1234”)
– NQE selects machine and forwards to NQS• Job remains pending (“NPend”) until resources available
– NQS runs the job• Assigns NQS request id (e.g., “5678.bhaskara”)
• Run job in appropriate batch queue
– Job log returned upon completion
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 5
• Libraries– Mathematics
• nag, imsl, slatec, lsode, harwell, etc.
– Graphics• ncar, gnuplot, etc.
– I/O• HDF, netCDF, etc.
– Applications• Amber, Ansys, Basis, Gamess, Gaussian, Nastran, etc.
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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PVP: Environment, part 6
• Tools– ja - job accounting– hpm - Hardware Performance Monitor– prof - Execution time profiler & viewer– flowtrace/flowview - Execution time profiler & viewer– atexpert - Autotasking performance predictor– f90 - Compiler feedback– totalview - Debugger (visual and line-oriented)
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: File Systems, part 1
• $HOME
– “permanent” (but not archival)
– 2 GB quota, regular backups, file migration
– poor performance for batch jobs• /u/repo/u10101• /Un/u10101• /u/ccc/u10101• /U0/u10101
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: File Systems, part 2
• $TMPDIR• temporary (created/destroyed each session)
• 75 GB quota (but NQS limits 4 GB - 32 GB)
• no backups, no migration– high-performance RAID arrays
– system manages this for you
– Can be used for parallel files
• /tmp• location of $TMPDIR• 14-day lifetime
• A.K.A. /big• you manage this for yourself
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: Environment, part 1
• UNICOS/mk
• Shells: sh/ksh, csh, tcsh– Supported:
• Sh• Csh• ksh (same as sh)
– Unsupported:• tcsh (get it by “module load tcsh”)
• Bash (get it by “module load tools”)
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: Environment, part 2
• Modules - manages user environment– Paths, Environment variables, Aliases, same as on PVP systems
• Cray’s PrgEnv is modules-driven
• Provided startup files are critical!– Add to .ext files, don’t clobber originals– Append to paths, don’t set them, and this only if necessary
– If you mess up, no compilers, etc.• Useful commands
• module list• module avail• module load modfile• module display modfile• module help modfile
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: Environment, part 3a
• Programming– Fortran 90: f90
– C/C++: cc, CC– Assembler: cam cam
– Use compiler (f90, cc, CC) for linking also
• Same naming conventions as on PVP systems– PGHPF - Portland group HPF
– KCC: Kuck and Assoc. C++;• Get it via “module load KCC”
• Multiprocessing– Execution in Single-Program, Multiple-Data (SPMD) Mode
– In Fortran 90, C, C++, all processors execute same program
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: Environment, part 3b• Executables - Malleable or Fixed
– specified in compilation and/or execution– f90 -Xnpes ... (e.g., -X64) creates “fixed” executable
• Always runs on same number of (application) processors
• Type ./a.out to run
– f90 -Xm... or without -X option creates “malleable” executable• ./a.out will run on command PE
• mpprun -n npes ./a.out runs on npes APP PEs
– Executing code can ask for:• Process id (from zero up)
– MPI_COMM_RANK(...)
• Total number of PEs– MPI_COMM_SIZE(...)
• PE or Process/Task ID used to establish “master/slave” identities, controlling execution
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
June, 2000 Introduction to NERSC - User Services Group
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T3E: Environment, part 4a• Execution modes
– Interactive serial• < 60 minutes on one command PE, 20 MW max memory
– Interactive parallel• < 30 minutes on < 64 processors, 29 MW memory per PE
– Batch queues
• To see them: qstat -b
• Queues shuffled in at night
• Subject to change
Pipe Queue Batch Queue MinPE
MaxPE
MPP Time Limit(seconds / hours)
Serial CPU TimeLimit
(seconds / hours)
serial serial_short 1 1 - 14400 / 4:00
debug_small 2 32 2000 / 0:33 3600 / 1:00debug
debug_medium 33 128 600 / 0:10 1800 / 0:30
pe16 2 16 15000 / 4:10 3600 / 1:00
pe32 17 32 15000 / 4:10 3600 / 1:00
pe64 33 64 15000 / 4:10 3600 / 1:00
pe128 65 128 15000 / 4:10 3600 / 1:00
pe256 129 256 15000 / 4:10 3600 / 1:00
production
pe512 257 512 15000 / 4:10 3600 / 1:00
long128 64 128 44200 / 12:17 3600 / 1:00long
long256 129 256 44200 / 12:17 3600 / 1:00
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T3E: Environment, part 4b• (Old, obsolete) Example of T3E management and queue scheduling
Time\pe's 0 128 256 384 512 640
01:00 PE512
03:00 PE256 PE128 pe128 Int32
07:00 Long128 PE128 PE64 PE64 PE32 PE32 Int64
19:00 GC 256 GC128 GC128 PE64
23:00 PE64
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T3E: Environment, part 5• Math & graphics libraries, and application codes are similar to
those on the PVP systems
• Libraries are needed for communication:– MPI (Message-Passing Interface)
– PVM (Parallel Virtual Machine)
– SHMEM (SHared MEMory; non-portable)
– BLACS (Basic Linear Algebra Communication Subprograms)
– ScaLAPACK (SCAlable [parts of] LAPACK)
– LIBSCI (including parallel FFTs), NAG, IMSL
• I/O libraries– Cray’s FFIO
– NetCDF (NETwork Common Data Format)
– HDF (Hierarchical Data Format)
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T3E: Environment, part 6
• Tools– Apprentice - finds performance problems and inefficiencies
– PAT - Performance analysis tool
– TAU - ACTS tuning and analysis utility
– Vampir - commercial trace generation and viewing utility
– Totalview - multiprocessing-aware debugger
– F90 - compiler feedback
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June, 2000 Introduction to NERSC - User Services Group
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SP: File Systems, part 1
• AIX is a Virtual Memory operating system – Each node has its own disks, with OS image, swap and paging
spaces, and scratch partitions .
• Two types of user-accessible file systems: – Large, globally accessible parallel file system, called GPFS
– Smaller node-local partitions
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SP: File Systems, part 2
• Environment variables identify directories – $HOME - your personal home directory
• Located in GPFS, so globally available to all jobs
• Home directories are not currently backed up!
• Quotas: 4 GB, and 5000 inodes
– $SCRATCH - one of your temporary spaces • Located in GPFS
• Very large - 3.5 TB
• Transient - purged after session or job termination
– $TMPDIR - another of your temporary spaces • Local to a node
• Small - only 1 GB
• Not particularly fast
• Transient - purged on termination of creating session or batch job
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SP: File Systems, part 3• Directly-specified directory paths can also be used
– /scratch - temporary space• Located in GPFS
• Very large
• Not purged at job termination
• Subject to immediate purge
• Quotas: 100 GB and 6000 inodes
• Your $SCRATCH directory is set up in /scratch/tmpdirs/{nodename}/tmpdir.{number}
where {number} is system-generated
– /scratch/{username} - user-created temporary space • Located in GPFS
• Large, fast, encouraged usage
• Not purged at job termination
• Subject to purge after 7 days, or as needed
• Quotas: 100 GB and 6000 inodes
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SP: File Systems, part 4
– /scr - temporary space • Local to a node
• Small - only 1 GB
• Your session-local $TMPDIR is set up in /scr/tmpdir.{number}where {number} is system-generated
• Not user-accessible, except for $TMPDIR
– /tmp - System-owned temporary space • Local to a node
• Very small - 65 MB
• Intended for use by utilities, such as vi for temporary files
• Dangerous - DO NOT USE!
• If filled up, it can cause the node to crash!
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SP: Environment, part 1
• IBM's AIX - a true virtual memory kernel – Not a single system image, as on the T3E
– Local implementation of module system
– No modules load by default
– Default shell is csh– Shell startup files (e.g., .login, .cshrc, etc.) are links; DON’T delete them!
– Customize extension files (e.g., .cshrc.ext), not startup files
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SP: Environment, part 2
• SP Idniosyncracies– All nodes have unique identities; different logins may put
you on different nodes– Must change password, shell, etc. on gsadmin node
– No incoming FTP allowed
– xterms should not originate on the SP
– Different sessions may be connected to different nodes
– High speed I/O is done differently from the T3E
– Processors are faster, but communication is slower, than on the T3E
– PFTP is faster than native FTP
– SSH access methods differ, slightly
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SP: Environment, part 3a• Programming in Fortran
– Fortran - Fortran 77, Fortran 90, and Fortran 95
– Multiple "versions" of the XLF compiler • xlf, xlf90 for ordinary serial code • xlf_r, xlf90_r for multithreaded code (shared memory parallelism) • mpxlf90, mpxlf90_r for MPI-based parallel code
– Currently, must specify separate temporary directory for Fortran-90 “modules”xlf90 -qmoddir=$TMPDIR -I$TMPDIR modulesource.F source.F
– IBM's HPF (xlhpf) is also available
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SP: Environment, part 3b
• Programming in C and C++ – C & C++ languages supported by IBM
– Multiple "versions" of the XLC compiler • cc, xlc for ordinary serial C code • xlC for ordinary serial C++ code • cc_r, xlc_r for multithreaded C code (shared memory parallelism) • xlC_r for multithreaded C++ code (shared memory parallelism) • mpcc for MPI-based parallel C code • mpCC for MPI-based parallel C++ code
– Kuck & Assoc. KCC also available in its own module
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SP: Environment, part 4a• Execution
– Many ways to run codes: • serial, parallel
• shared-memory parallel, message-based parallel, hybrid • interactive, batch
– Serial execution is easy:./a.out <input_file >output_file
– Parallel execution - SPMD Mode, as with T3E • Uses POE, a supra-OS resource manager
• Uses Loadleveler to schedule execution
• There is some overlap in options specifiable to POE and LoadLeveler
• You can use one or both processors on each node– environment variables and batch options control this
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SP: Environment, part 4b– Shared memory parallel execution
• Within a node, only
• OpenMP, Posix Threads, IBM SMP directives
– Message-based parallel execution • Across nodes and within a node
• MPI , PVM, LAPI, SHMEM (planned)
– Hybrid parallel execution• Threading and message passing
• Most likely to succeed: OpenMP and MPI
– Currently, MPI understands inter- vs. intra-node communication, and sends intra-node messages efficiently
NATIONAL ENERGY RESEARCH SCIENTIFIC COMPUTING CENTER
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SP: Environment, part 4c– Interactive execution
• Interactive jobs run on login nodes or compute nodes
• currently, there are 8 login nodes
– Serial execution is easy:./a.out <input_file >output_file
– Parallel exeuction involves POE:poe ./a.out -procs 4 <input_file >output_file
• Interactive parallel jobs may be rejected due to resource scarcity; no queueing
• By default, parallel interactive jobs use both processors on each node
– Batch execution • Batch jobs run on the compute nodes
• By default, parallel batch jobs use both processors on each node;– you will be charged for both, even if you override this
• Use Loadleveler utilities set to submit, monitor, cancel, etc.
– requires a script, specifying resource usage details, execution parameters, etc.
– Several job classes, for charging, resource limits: premium, regular, low;
– two job types - serial and parallel
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SP: Environment, part 4d• SP Batch Queues and resource Limits
• Limits:– 3 jobs running
– 10 jobs considered for scheduling (idle)
– 30 jobs submitted
Class Max Nodes Max Processors Max Time Priority
debug 16 32 30 minutes 20000
premium 256 512 4 hours 10000
regular 256 512 4 hours 5000
low 256 512 4 hours 1
interactive 8 16 20 minutes 15000
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SP: Environment, part 5
• Libraries and Other Software– Java, Assembler
– Aztec, PETSc, ScaLAPACK
– Emacs
– Gaussian 98, NWChem
– GNU Utilities
– HDF, netCDF
– IMSL, NAG, LAPACK
– MASS, ESSL, PESSL
– NCAR Graphics
– TCL/TK
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SP: Environment, part 6• Tools
– VT - vsualization tool for trace visualization and performance monitoring
– Xprofiler - graphical code structure and execution time monitoring
– Totalview - multiprocessing-aware debugger
– Other Debugging Tools• Totalview - available in its own MODULE;
• adb - general purpose debugger
• dbx - symbolic debugger for C, C++, Pascal, and FORTRAN programs
• pdbx - based on dbx, with functionality for parallel programming
– TAU - ACTS tuning and analysis utility - planned!
– Vampir - commercial trace generation and viewing utility - future!
– KAP Suite - future?
– PAPI - future?
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HPSS Mass Storage
• HPSS– Hierarchical, flexible, powerful, performance-oriented
– Multiple user interfaces allow easy, flexible storage management
– Two distinct physical library systems• May be logically merged in future software release
– Accessible from any system from inside or outside NERSC• hpss.nersc.gov, archive.nersc.gov (from outside NERSC)• hpss, archive (from inside NERSC)
– Accessible via several utilities• HSI, PFTP, FTP
• Can be accessed interactively or from batch jobs
• Compatible with system maintenance utilities (“sleepers”)
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HPSS Mass Storage• HPSS
– Allocated and accounted, just like CPU resources• Storage Resource Units (SRU’s)
• Open ended - you get charged, but not cut off, if you exceed your allocation
• “Project” spaces available, for easy group collaboration
– Used for system backups and user archives• hpss used for both purposes• archive is for user use only
– Has modern access control• DCE allows automatic authentication
• Special DCE accounts needed
– Not uniformly accessible from all NERSC systems• Problems with PFTP on the SP system
– Modern secure access methods are problematic• ftp tunneling doesn’t work (yet…)
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Accessing NERSC• NERSC recognizes two connection contexts:
– Interaction (working on a computer)
– File transfer
• Use of SSH is required for interaction (telnet, rlogin are prohibited)– SSH is (mostly) standardized and widely available
– Most Unix & Linux systems come with it
– Commercial (and some freeware) versions available for Windows, Macs,
– SSH allows telnet-like terminal sessions, but protects account name and password with encryption
• simple and transparent to set up and use
• Can look and act like rlogin
– SSH can forward xterm connections• sets up a special “DISPLAY” environment variable
• encrypts the entire session, in both directions
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Accessing NERSC• SSH is encouraged for file transfers
– SSH contains “scp”, which acts like “rcp”– scp encrypts login info and all transferred data
– SSH also allows secure control connections through “tunneling” or “forwarding”
– Here’s how tunneling is done:• Set up a terminal connection to a remote host with port forwarding enabled
• This specifies a port on your workstation that ssh will forward to another host
• FTP to the forwarded port - looks like you are ftp’ing to your own workstation
• Control connection (login process) is forwarded encrypted
• Data connections proceed as any ftp transfer would, unencrypted
• Ongoing SSH issues being investigated by NERSC staff– Not all firewalls allow ftp tunneling, without “passive” mode
– HPSS won’t accept tunneled ftp connections
– Workstation platform affects tunneling method
– Methods differ slightly on the SP• New options, must use xterm forwarding, no ftp tunneling...
– Different platforms accept different ciphers
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Information Sources - NERSC Web Pages
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Information Sources - On-Line Lecture Materials