Disk reservation

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Disk reservation is a technique to reserve hard disks on Grid'5000, in order to store large datasets between your nodes reservations, and avoid moving data to nodes at the beginning of each nodes reservations.

During the beta testing phase, disks reservation will only be available on the grimoire cluster. The service will be extended to other clusters afterwards.

Site Cluster Number of nodes Number of bookable disks per node
Nancy grimoire 8 5
Warning.png Warning

Disk reservation is an experimental service and data integrity is not guaranteed. You MUST backup your important data.

How it works

Disk reservation works with jobs of type noop (being not mandatory) and jobs of type deploy. You can reserve some disks in the long run with a job of type noop. Then, you may reserve the nodes where your disks are located with a job of type deploy.

When the job of type deploy starts, the disks you reserved are enabled by the RAID card of the node, and the other disks are disabled. Reserved disks can only be accessed by the user who reserved them (see also Security issues).

Usage

The main commands to reserve disks are given below. Note that disk reservation only works with a node reservation of type deploy. By default, reserving a node on grimoire will only grant access to the main disk (additional disks need to be reserved).

The maximum duration of a disk reservation (job of type noop) is defined in the Usage Policy.

Reserve disks and nodes at the same time

Reserve a node with its main disk on the grimoire cluster:

Terminal.png fnancy:
oarsub -I -t deploy -l {"cluster='grimoire'"}/host=1

Or reserve a node with all its disks:

Terminal.png fnancy:
oarsub -I -t deploy -l {"type='disk' or type='default' and disk_reservation_count > 0"}/host=1

disk_reservation_count is equal to the number of bookable disks on a node.

Reserve nodes grimoire-1 and grimoire-2 with one reservable disk per node:

Terminal.png fnancy:
oarsub -I -t deploy -l {"type='default' and host in ('grimoire-1.nancy.grid5000.fr','grimoire-2.nancy.grid5000.fr')"}/host=2+{"type='disk' and host in ('grimoire-1.nancy.grid5000.fr','grimoire-2.nancy.grid5000.fr')"}/host=2/disk=1

Reserve disks and nodes separately

First : reserve the disks

For example, you may decide to reserve some disks for one week, and the nodes where your disks are located only when you want to carry out an experiment. Jobs of type noop are used to reserve disks. They cannot be interactive and are necessarily reserved in advance.

Reserve two disks on grimoire-1 for one week, starting on January 1st 2018:

Terminal.png fnancy:
oarsub -r "2018-01-01 00:00:00" -t noop -l {"type='disk' and host='grimoire-1.nancy.grid5000.fr'"}/host=1/disk=2,walltime=168

Reserve the first two disks on grimoire-2:

Terminal.png fnancy:
oarsub -r "2018-01-01 00:00:00" -t noop -l {"type='disk' and host='grimoire-2.nancy.grid5000.fr' and disk in ('1', '2')"}/host=1/disk=2,walltime=168

Or reserve all disks on two nodes:

Terminal.png fnancy:
oarsub -r "2018-01-01 00:00:00" -t noop -l {"type='disk' and cluster='grimoire'"}/host=2/disk=ALL,walltime=168

Secondly: reserve the nodes

You can reserve nodes grimoire-1 and grimoire-2 for 3 hours, in the usual way:

Terminal.png fnancy:
oarsub -I -t deploy -l {"host in ('grimoire-1.nancy.grid5000.fr', 'grimoire-2.nancy.grid5000.fr')"}/host=2,walltime=3

You must respect this order : reserve the disks first, then reserve the nodes. Otherwise the disks you reserved will not be available on your nodes.

Security issues

Grid'5000 being a platform of the type "hardware as a service", it is not possible to avoid a malicious user to take control of the RAID card and therefore of the disks. If you have sensitive data and don't know how to protect them, you may contact the Grid'5000 technical team to help you. It is also your responsibility to erase the data on the disks you reserved, at the end of your experiment.