Database Reference
In-Depth Information
Some organizations pre-assign spaces for certain usage, and the space
tokens are made known to those permitted to use them.
In practice, allocating space to individual users requires a complicated
allocation scheme where the amount of space used by each individual is
controlled and monitored by the organization that owns the storage and
compute resources, referred to as the virtual organization (VO). While
SRMs can be expected to keep track and enforce space usage, they can-
not be expected to implement various policies. Therefore, many organi-
zations choose to manage space for groups of users, expecting each user
in that group to behave responsibly and not “hog” the entire space. On
the other side of the spectrum, SRMs can use quotas by default, which
are specified in a
configuration file
. If all users accessing an SRM have
the same privileges in terms of space quotas, this is sucient. However,
experience shows that it will be beneficial to assign quota privileges for
individuals in storage space allocated to a group. Such a possibility is not
available in the latest SRM v2.2 specification, as noted in Section 3.4.
13. Directory management.
The initial version of the SRM specification
assumed that it is not necessary to provide clients with the ability to
organize their files and that the SRM can assign its own directory struc-
ture. Typically, a single flat directory was assigned for each user. How-
ever, as the number of users, groups, and projects grew, it became ob-
vious that the support of a directory structure and functions similar to
those supported by Unix as well as access control lists (ACLs) is needed.
Thus, the usual functions of ls, mkdir, rmdir, mv, rm, and cp were added
to the SRM specification. However, given the ability to have multiple
spaces, the question was whether each space can have its own directory
structure.
The conclusion to this question was that there should be a single di-
rectory for all spaces owned by a virtual organization. Furthermore, files,
assignments to spaces is a property of the files, and therefore when a file
is moved from one space to another, there is no effect on the directory
structure; that is, the file stays in the same position in the directory. The
important advantage of this choice is that files can be moved between
spaces without effect on their path names.
A similar question arose about file types. Should all file types be sep-
arated into different directory structures? Here, too, the conclusion was
that file types are the property of the file, and therefore a file can be
changed, for example, from volatile to permanent without any effect on
the directory structure and the file path name.
3.3.3 Conclusion
The description of the SRM functionality provided in this section makes it
clear that the decisions on what to include in the standard specification are
