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en:linux-gestion-espace-disque

Disk space management

Used/Available disk space ?

If you type the command line

cd ~; df -h .

It will show you this kind of informations :

Sys. de fich. Tail. Occ. Disp. %Occ. Monté sur atlantide:/atlantide/pierreg 24G 4,5G 20G 19% /home/pierreg

The 1st column indicates in which server your account is located, the 2nd column shows which disk space is still available in your account. The 3rd indicates the disk space used.

Account backup snapshots

Snapshots of each account are taken every hour, every day and Every month.

Snapshots are taken in order to allow users to recover files deleted by mistake.

The way it works is that before each snapshot, the system keeps track of the list of files in the account.

If a file is deleted and is not in the list of any of the snapshots the disk space allocated to the file is liberated otherwise it is kept so that it can be recovered later.

Comme la création des images est cyclique, éventuellement l'espace sera récupéré, mais cela peut prendre plus ou moins de temps selon le moment où le fichier est créé et le moment où il a été effacé.

For example, if you create a temporary file for a calculation at 10:25. When the calculation is done at 10:45 the temporary file gets deleted. No snapshot was taken during this time, so the disk space used by the temporary file gets free again.

If you create another temporary file at 10:25 but this time your calculation took like 6 hours. During this laps of time snapshots at 11:00, 12:00, …, 18:00 were taken. When the simulation is over the temporary file gets erased BUT the reference to the file still exists ( you can still recover it). The reference to this file will exist until the next day at 18:00 after that the disk space allocated to this file will be free again. Donc à 18:00 le lendemain soir il n'y a plus de référence et l'espace peut être libéré. Same thing for daily and monthly snapshots. It take between 30 to 60 days to free a space from a daily snapshot. and a year to free the space from a file on monthly snapshot.

It is then possible to clean up your account and free disk space in your account.

How to use temporary directory /tmp

Every UNIX machine has a /tmp directory used for temporary files. It is very important not to put important files in this directory because the operating system can erase them when they are not used for a while. It also not subject to snapshots or backups.

This disk space is not part of your personal quota.

We strongly recommend that you create temporary files used in your calculation in this directory and use the data output in your account.

en/linux-gestion-espace-disque.txt · Last modified: 2016/04/04 13:03 by admin