In this video, you will learn about block volume replicas and boot volume replicas. This is a new feature introduced on April 6th, 2021. The idea behind replicas is a useful scenario when you want to have a continuous replication of data in your volume to another region to take care of DR, or movement scenarios. You might have volumes in one region and you want to replicate that to another region. This is a typical use case. Remember, we have already seen the idea of using clones which is a NAD operation, the idea of backups within the current data in a block volume or boot volume can be copied as a snapshot into objects storage and use it to create new volumes within the same region in NAD. Or copy the backup to another region and create new volumes in the other region. This gives you an even better functionality because backups are point in time, clones are point in time thereafter, if you want the source and destination to be in sync, you are supposed to implement it by attaching the volume to a compute instance and doing OLS label replication. Whereas with block volume replicas at the storage level, your data is automatically replicated to another region. How do we do that? If you go to a given block volume, for example, and edit the volume, you get the ability to see whether you want cross-region replication to be turned on. By default, when you create a volume it is off, or when you create a volume itself, you have the ability to enable cross-region replication. If you have an existing volume and you enable cross-region replication by editing it, you will be given the choice to choose the destination region. Now, the destination region that you can use depends on which is the source region. They are tied from a particular region. You can only replicate to a particular region or a particular set of regions which is predetermined by Oracle. As a tenant, you must be subscribed to the destination region for you to be able to enable cross-region replication. You can choose the AD and the name for the target volume. Let's say cloned volume, instead, I will call it as replica from Frankfurt. As you can see in the console here, once this feature is enabled, the volume will be replicated to the AD and region that you choose. Your bill will include applicable block storage cost from that region, as well as the cross-region network transport that is applicable. You need to accept it and save changes. As a result of this, if I see further replicas in Frankfurt, there might be none. But if I go to the destination region, I will see that a replica is getting created. If I click on the replica volume that is getting created, I will get to see how much of that data has been transferred. It might take a few hours to replicate the data, depending on the size of the data in the source volume, the initial transfer will take quite a number of hours or days depending on the source and destination region. Once the initial sync up is in place, it will continuously sync any changes getting in the source region to the target region. Again here, volumes which are having heavy IO operations to perform rates might have a delay in the sync up because it is a wide area network of between region connectivity, it is not guaranteed that there will be no data loss in case the primary region fails. This is an additional functionality that you can use to take care of synchronizing volumes across regions. At any given time, if you want to activate this, you can activate it. The moment you activate it, you need to realize that synchronization stops and then you can use this volume in the region where it is created. When you have a replica getting created from a volume, you will not be able to increase its size. I think I enabled replication for this volume. If you try to increase the size, it might error out because it doesn't support increase in size when you have replica enabled. If you want to increase the size of the source volume you need to disable. When you disable the cross-region replication, please note that destination replica is deleted. You can increase the size and again enable a replica for it. That is the way this functionality works. In the same way, even for boot volumes you can go and edit the boot volume to have a cross-region replica to be created. If you have it on in the destination region in the destination AD the replica will be available. If I go to London, I should see under boot volume replicas, a replica getting created. In this case, we can see how much data is transferred, only three GB is transferred. The last sync happened at this point in time, the initial sync up will take a considerable amount of time depending on the amount of data that is present in the source volume. This feature is an additional feature compared to backups and cloning that we saw as part of block storage. This functionality gives you a third option to keep your VR considerations in mind. That's about block volume and boot volume replicas as a feature within block storage.
