Use object storage if you want S3-compatible storage for files and backups. Use a volume if the server needs an extra disk.
A volume is a block device attached to a VM. Object storage is S3-compatible: buckets and objects, reached over the API. Typical uses are application backups, media, static assets, and datasets. The first 100 GB is free each month. The Sioux Falls endpoint is files.fsd1.gozunga.com.
Cloud → Object Storage is the inventory in the portal. Create the bucket here. Large uploads go through the S3 API, not the portal. Portal uploads are size-limited.
If the guest needs a filesystem it can mkfs and mount, that is a volume. See Storage Options.
Open Cloud → Object Storage. Click + Create bucket. The table shows Name, Size, Created At, and Region. An empty project says No Rows To Show.
Create access keys under Cloud → Access → S3/EC2 Credentials. Point the client at files.fsd1.gozunga.com. s3cmd needs signature_v2 = True. Full client setup:
Related: Snapshots and backups when the copy you need is a disk, not a file.