dpturner_at_rasta.nersc.gov
Date: 06/20/2002
Greetings NERSC Cray User,
As you know, NERSC is planning to retire its remaining Cray computers
this October 1. One of the issues we are investigating is the fate
of users' on-line files. User files in /tmp and /usr/tmp will be
permanently lost, but we expect that files in $HOME will be preserved
in HPSS. This email is the first in a series that will address how
users can help NERSC in this effort.
Files in $HOME can be either on disk, or "migrated" to tape (in HPSS).
As of early May 2002, Killeen had about 132,000 migrated files, totaling
about 721GB; the numbers for MCurie were 32,000 files totaling 326GB.
Migrated files count against users' quotas (both inode and space). Many
users have migrated files that have not been accessed in over a year.
We would like to request that all users begin reviewing their migrated
files, with the objective of deleting files that are no longer needed
(if, for example, copies of the files have already been stored in HPSS,
or the files have become obsolete).
This needs to be done with some care. What we DON'T want to happen is
for many users to un-migrate lots of files simultaneously. This can put
a heavy strain on HPSS (for example, causing delays for batch jobs that
are saving results). More seriously, any large un-migration of files will
quickly fill the available disk space in $HOME, causing additional files
to migrate. Therefore, we are asking users to delete only migrated files
that can be determined to be unnecessary WITHOUT un-migrating them.
Commands that need to access the CONTENTS of a file will automatically
cause a migrated file to un-migrate. These commands include text editors
(vi, emacs, tedi), the "file" command, the "cp" command, and any user
programs that read the file. However, often it is sufficient to just
know the name and timestamp of a file to determine its value. Examples of
commands that can access files WITHOUT causing un-migration include the
"ls" command, the "mv" command, the "rm" command, and some uses of the
"find" command.
A useful way to get a complete listing of all the migrated files in your
home directory is to use the following commands:
cd $HOME; /bin/find . \( -type m -o -type M \) -print
Note that depending on the size of your $HOME and the number of migrated
files, this command might take some time to run, and might produce a large
amount of output. Users are encouraged to use the above commands to begin
the process of identifying and deleting unneeded migrated files.
If you have any questions regarding migrated files, please contact NERSC
consulting at:
Web: http://help.nersc.gov
Email: consult@nersc.gov
Phone: 1-800-66-NERSC, menu option 3
1-510-486-8600, menu option 3
Best regards,
David Turner
User Services Group email: dpturner@nersc.gov
NERSC Division phone: (510) 486-4027
Lawrence Berkeley Lab fax: (510) 486-4316
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