Answers to some questions about using NeCTAR object store for backups.

These questions come from a user, and the answers are from Edan Scriven (with some additions ...)

How big can an Object Store be?

This is ultimately limited by the size of the storage cluster, so about 40TB.

How many objects can be created ?

OpenStack doesn't implement quotas, so users can keep creating objects until they fill the pool. They'll notice performance loss if they put more than a couple thousand files into one container though.

Is there a restriction on data size ?

No, though in practice due to limits in HTTP it is not recommended to transfer files bigger than 1GB via the dashboard. The command-line swift client has a means of breaking files into pieces to transfer larger files. 

Also remember the dashboard only interfaces to the Melbourne swift region, and you will need to use the command-line tool anyway to access the Qld region.

(A NeCTAR "allocation request" includes a place where you can request Object Storage, but in practice, you can use it, irrespective of whether you formally requested it or not.)

Where are the objects backed up ? Is the object store a suitable form of storage for backups?

The objects are stored in triplicate on the swift cluster, but that only provides fault tolerance and there is no other backup process for the files stored there. You can store a VM there by taking a snapshot, downloading the snapshot file and uploading it to swift. However, the snapshot is stored in the glance image repository in Melbourne too, and this may be sufficient.

(Note that backup-by-replication means that you are unlikely to be able to get an "old version" of a given Object Store object. But you can get around this by using different objects to hold snapshots of something taken at different times ... modulo practical usage limits.   Whether this is adequate for your needs is for you to judge.)

If NeCTAR goes down, is the object container data still accessible ?

Mostly. The only federal NeCTAR component that is required for access to Swift is Keystone, the authentication service. If Keystone is down, you will not be able to access the object store, but note that all other OpenStack functions would be offline as well.

See also: