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File Storage

Disk Quota Change Request Form

Carver File Systems

Carver has 3 kinds of file systems available to users: home directories, scratch directories and project directories, all provided by the NERSC Global File system. Each file system serves a different purpose.

File SystemHomeScratchProject
$HOME $SCRATCH or $GSCRATCH No environment variable
  • Global homes file system shared by all NERSC systems except PDSF.
  • Where users land when they log into the system.
  • Global scratch file system shared by all NERSC systems except Franklin and PDSF.
  • Global project directories shared by all NERSC systems.
Default Quota
  • 40 GB
  • 1 million inodes
  • 20 TB
  • 2 million inodes
  • 1 TB
  • 1 million inodes
Intended Purpose
  • Shell initializations
  • Storing source code
  • Compiling codes
  • Not intended for I/O intensive applications
  • Running production applications
  • I/O intensive jobs
  • Temorary storage of large files
  • Running production applications
  • Groups needing shared data access
  • Projects running on multiple NERSC machines
Peak Performance Low, ~100 MB/sec 15 GB/sec 40 GB/sec
Purged? No Yes, files older than 12 weeks are purged No

Home Directories

Upon logging in, users are placed in their home directory by default. Home directories are limited in size and are meant for permanent storage of source code and other relatively small files. This file system is not configured for high I/O performance.

Home directories should always be referred to by the environment variable $HOME. The absolute path to a home directory (e.g., /u4/joe/) may change, but the value of $HOME will always be correct.

Please back up all important files on a regular basis.

For security reasons, never allow "world write" access to the directories $HOME or $HOME/.ssh. NERSC scans for such security weakness, and, if detected, will change the permissions on the directories to disable "world write" access. Furthermore, SSH will not allow you to login if $HOME/.ssh is writeable by anyone other than you.

Home directories contain various shell initialization files ("dot-files", e.g. .login, .cshrc, .profile). These are symbolic links to NERSC-defined and controlled files that contain definitions needed by all users. Please do not not remove or modify these links. Customizations of login behavior can be specified in "extension" files with names such as .login.ext, .cshrc.ext, and .profile.ext.  See Global Homes.

Scratch Directories

The contents of $SCRATCH will be deleted ("purged") as needed as the system's disks approach capacity.You should back up your important files frequently to HPSS.

Project Directories

Project directories provide a large-capacity file storage resource that is intended for groups of users ("projects") that desire to share data among themselves and/or between major compute platforms. Note that this definition of project may include users from multiple NERSC repositories. See Project Directories.

Do Not Use /tmp Explicitly

WARNING: Do not attempt to explicitly use the file system named /tmp. Your job may fail or be deleted if it writes to /tmp.

Some software tools (editors, compilers, etc.) use the location specified by the $TMPDIR environment variable to store temporary files. Additionally, Fortran codes which open files with status="scratch" will write those files into $TMPDIR. On many Unix systems, $TMPDIR is set to /tmp. NERSC has set $TMPDIR to be $SCRATCH. Please do not redefine $TMPDIR!