HOME
Every user gets a HOME directory.
Its path is always stored in the environmental variable $HOME and most shells will expand ~ into it.
The directory will be HOME_BASE/ACADEMIC_CLOUD_USERNAME/USER where HOME_BASE is one of the base directories for home directories (there is more than one and they may change in the future).
The base directory shown by POSIX commands (like getent passwd) or in the environment variables can be a symbolic link (e.g. /user/jdoe1/u12345), which points to the actual base directory on the data store (e.g. /mnt/vast-nhr/home), or another link farm (/mnt/vast-orga) which only contains symlinks to the real home directories.
The HOME directory is meant for a user’s:
- configuration files
- source code
- self-built software
The HOME storage systems have the following characteristics:
- Optimized for a high number of files rather than capacity
- Optimized for robustness rather than performance
- Has limited disk space per user
- Is regularly backed up to tape (most also have snapshots, see below)
- Has a quota
The HOME filesystems have slow-medium to medium performance. The HOME directories for each kind of user are given in the table below.
| Kind of User | Media | Capacity | Filesystem |
|---|---|---|---|
| all | SSD | 1.15 PiB (shared)(comp)(dedup) | VAST exported via NFS |
Info
Legend for the tags in the Capcity column:
(shared): They share capacity with other data stores. For example, NHR HOME and Project data stores are on the same storage system.
(comp): Use live compression to increase effective capacity, though this comes at the expense of some CPU time to compress and decompress.
(dedup): Use deduplication to increase effective capacity.
Snapshots
If you accidentally deleted or overwrote something in your home directory and want to restore an earlier version of the affected files, it is not generally necessary to write a ticket.
The home filesystems save regular snapshots that are kept for a short period (currently 30 days of daily snapshots).
These snapshots can be accessed for any directory by entering the hidden .snapshot directory by cd .snapshot.
Info
The .snapshot directories are “hidden” on a deep level, so that they don’t even show up with ls -a, and thus autocomplete on the command line does not work for them.
They are implemented this way on VAST filesystems, so they can be accessed everywhere, for every (sub-)directory, and are not included when copying or moving directories to another location.