The file system and physical locations on Holodeck

The main storage of Holodeck is physically located on the head nodes and split into two parts. One is called export and is only accessible on the head nodes, the other one is called holohome and synchronized across all nodes. These storage locations are visualized in the graphic below. A file system written in dark grey is not physically located on that node but only accessible. The arrows than point to the physical location. All nodes called nr<x> are the work nodes and have a local storage each. To see all available directories and their available sizes type

df -h

where the “-h” flag shows the sizes in a humanly readable way.

Guide to data storage

The idea with the different partitions is for them to be used in different ways. Usually you will only want to use /holohome and /export and leave the /local directories alone, as they are not synced between all machines.

The purpose of /holohome is to be the main storage for everything you want to work on at the moments. Therefore your code should write to and read from this partition. This should not cause any major speed disadvantages over the local storage as the work nodes are connected to the head nodes with a very fast inifiniband network connection.

The purpose of /export is to be a place for archiving. The plan is to have a backup software run on this partition and hence the space on there could be more limited at some point. Therefore place only the cleaned data from the runs you won’t be accessing too often anymore here. (i.e. when a project is finished. Also consider entering the project into this list.)

See also

List of nodes on Holodeck · Simple code example · List of publications using Holodeck

-- MarlinSchFer - 18 Apr 2019