Colt will eventually use the Distributed Computing Environment (DCE)
for user authentication. With DCE, all user information is centralized
in the "registry", so each system in a DCE "cell" does not require a separate
copy of each user's login information
("/etc/passwd"). Integrated with DCE is the Distributed File
System (DFS). Though DCE is not yet available, DFS is accessible from all nodes
of Colt through NFS mounts. Because of the NFS intermediation, users must
take special steps to write to DFS.
When you first log in, and at regular (~monthly) intervals
afterwards, you will need to issue the following commands on Colt. You
should not have to issue these commands every time you log in (unless
you only log in once a month).
$ kinit
Password for user@dce.ccs.ornl.gov: password
$ dfs_login
DCE password for user: password
...
Because the DFS servers are external to Colt, DFS does
not provide the highest performance. For fast file access on Colt,
see PFS, below.
All user home directories are kept in DFS, and each user
has a default storage limit of 500 MB. In addition to the
"yesterday" backup described below, home
directories in DFS are copied to tape backup four times a week.
Each home directory has a
default set of subdirectories:
| public | This directory is world readable. Use
it to make files available to other users of Colt. |
| private | This directory is only accessible by
the user. |
| yesterday | This directory contains a read-only
copy of all the rest of the home directory, including other
subdirectories, as of the day before. The copy is generated at 4 AM
each morning. If you accidentally delete any of your DFS files, you
can simply copy
versions from the day before out of "yesterday". |
| bin | This directory is a default
location for user-generated executables. It is not in your
"PATH" by default, however. You can add it or one if
its subdirectories to your "PATH" in your ".profile"
or ".cshrc" file. |
| www | In the future, we plan to make all
documents kept in this directory available over the World-Wide
Web. |
For more information on DCE and DFS, see online documentation
from IBM, available at the following URL.
http://www-4.ibm.com/software/network/dce/library/publications/dceaix.html
The Parallel File System (PFS) is a temporary-storage area
with shared access from all Colt nodes. For large files, PFS is the
highest-performance file system available on Colt. The PFS servers
are nodes of Colt, and data transfer goes exclusively over
the Quadrics Elan interconnect.
PFS is intended as work space for Colt applications. PFS is not
backed up, so you need to copy any important output from PFS to one
of the other file systems for permanent storage. Currently, there is
only one PFS partition, "/pfs1". Additional partitions, with
different topologies, are planned for the near future.
The High-Performance Storage System (HPSS) provides archival
storage. It is "high performance" relative to other archival systems,
not relative to native file systems like PFS. Large permanent files
should be moved directly from PFS, presumably where they were
created, to HPSS.
You access HPSS through the "hsi" interface. This
interface is available on all AlphaServer nodes. When used with DCE authentication, "hsi" requires
no password and can thus be used within batch scripts. DCE is not yet
supported on Colt, however. (But neither is a batch system!)
For more information on HPSS and "hsi", type "hsi
help" or see the online
documentation kept at SDSC, available at the following URL.
http://www.sdsc.edu/Storage/hsi/
