In StoreGrid Cloud AMIs, the Backup Server will receive the backup data from the clients and store the data in EBS volumes (as a temporary cache location) and upload the data to Amazon S3. Please note that, the EBS volume which we use as a temporary storage is also a persistent to store your backed up data.
Even, if the EC2 instance is stopped, the EBS volume will not be affected and the data will be intact with the EBS volume.
If your EC2 instance is stopped, you can create a new EC2 instance and attach the existing EBS volume to your EC2 instance . All your StoreGrid configurations and temporary cache data will be intact with the new EC2 instance. For redundant backups of the EBS you can also configure periodic snapshots for the EBS volumes by using StoreGrid. For that, you need to enable Snapshots in the SGConf.xml file present in the '<Mounted_Location>/SGCloudConf' location and specify the snapshot configuration in SGConf.xml file.
Please refer the following URL to get more details about configuring StoreGrid EC2 instance: http://www.vembu.com/storegrid/amazon-ec2-s3-cloud-online-backup.php