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AFS Volumes

An AFS volume is analogous to a filesystem on a logical partition. Volumes are mounted at some point in the AFS filesystem hierarchy, at which point they become available to client computers. Volumes are the unit of AFS server space for transactions such as creation, deletion, migration between servers, replication, and backups. Volumes can be any size up to the physical size of the server disk partitions, but many operations on volumes are easier if the size is kept smaller.

Volumes may be mounted anywhere in AFS space, including multiple mount points (although this is confusing). Disk quotas are applied at the volume level. The command to check on the current quota status is subcommand listquota to fs, i.e. fs_listquota. Less detail

The ACL (Access Control List) at the top level of the volume is important, since it may be mounted in a location with less restrictive parent ACLs than intended. For example, a user volume might be inaccessible to unauthenticated users by being mounted below a private directory. If the volume itself allows public read, it may be re-mounted inside a public directory and lose the protection.

Typically we use:

Two special volumes always exist, and are replicated onto each file server for redundancy.

When a program opens a file, the AFS client must first look up the location of the volume containing the file, then connect to the appropriate file server. When listing directory contents containing many volume mount points, many database lookups are needed. This metadata is cached, but performance can still be slow (e.g. ls -l /afs/northstar/ufac). Unfortunately GUI file managers love to do this, frequently.

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