Chapter 3: PNFS Namespace
3.1 UNIX Commands You can Use in PNFS Space
Data files do not actually reside in /pnfs namespace, and errors occur on attempts to read or write the content of the files, or to manipulate the content. Therefore, UNIX commands such as cat, more, less, grep, head, tail, wc, od, file, cp, and so on, fail if you run them on files listed under /pnfs. However, virtually any non-I/O UNIX command can be used in /pnfs namespace. For these commands, the standard options work in the standard way. Commands that you may find useful include:
For ln, hard links must be used to ensure that all the metadata information is linked; symbolic links do not work properly .
Stat is not available in all operating systems.
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3.2 About PNFS Tags
Before files can be written to tape, Enstore needs to know where and how to write them. Pnfs uses tag files (usually just called tags) in the /pnfs namespace to specify this type of configuration information, and encp transfers this information to Enstore. Tags are associated with directories in the /pnfs namespace, not with any specific file, and thus apply to all files within a given directory. As a new directory in the /pnfs namespace is created, it inherits the tags of its parent directory. Allowable characters within tags are: alphanumeric characters, underscore ( _ ), dash ( - ), and slash ( / ).
3.2.1 Tag Listing
The tags include:
- file_family
- This tag determines the file family associated with all
files in this directory. See section 1.4.1 File Family for
information on file families.
- file_family_width
- This tag determines the file family width associated
with all files in this directory. See section 1.4.2 File
Family Width for information on file family width.
- file_family_wrapper
- This tag determines the file family wrapper associated
with all files in this directory. See section 1.4.3 File
Family Wrapper for information on file family
wrappers. The default is cpio_odc.
- library
- This tag determines the virtual library (and thus the
library manager) associated with all files in this
directory. See section 7.3 Library Manager for
information about the library.
- storage_group
- This tag determines the storage group associated with
all files in this directory, and shows up as your
experiment's top level directory under /pnfs.
Typically, one storage group is associated with an entire
experiment. A storage group is assigned to each
experiment by the Enstore administrators. Users never
change this tag.
3.2.2 How to View Tags
Off-site users cannot mount pnfs, and therefore cannot see tags. On-site users: to see the values of the tags for a given directory, first setup encp (with qualifier, see section 5.1 Setup encp) then cd to the /pnfs subdirectory of interest (or enter the directory as an argument to --tags) and enter the command:
% enstore pnfs --tags
.(tag)(file_family) = dcache
.(tag)(file_family_width) = 1
.(tag)(file_family_wrapper) = cpio_odc
.(tag)(library) = eagle
.(tag)(storage_group) = test
-rw-rw-r-- 11 xyz sys 6 Jul 26 10:22 .(tag)(file_family)
-rw-rw-r-- 11 xyz sys 1 May 5 2000 .(tag)(file_family_width)
-rw-rw-r-- 11 xyz sys 8 May 5 2000 .(tag)(file_family_wrapper)
-rw-rw-r-- 11 xyz sys 5 May 5 2000 .(tag)(library)
-rw-r--r-- 11 xyz sys 4 Jul 26 10:20 .(tag)(storage_group)
The output first lists the tags and their values, then the tags again in long format to show the owners and protection modes.
Enstore and dCache User
Documentation
