- Now let's talk about EBS Snapshots.
EBS Snapshots are a tool that we can use to increase
the durability of the data stored on our EBS volumes.
Now EBS volumes are in a number of ways a really great
tool to use within AWS just because they're independent
from the life of the EC2 Winstons,
we have a lot of control over
the performance of that volume,
but they do exist in a single availability zone.
And while they are durable,
they have some degree of resilience,
they're resilient to the loss of
a device within the cluster,
they are not durable to the loss of an availability zone.
So going back to our fundamental architectural question,
what happens when this device fails?
What happens when we lose an availability zone?
Even though it might be rare,
it can still happen, we have to plan for it,
what happens when we lose an availability zone?
Then we should have a good answer to that,
and the answer is well, we have Snapshots of that volume
that are stored in S3 which is inherently highly available,
S3 is durable to the loss of up to two AZs,
so that means our data is still there,
and we can recreate that volume from
that Snapshot in another availability zone.
So when we take a Snapshot,
let's say we take a Snapshot of this volume,
that Snapshot will be stored over here in S3.
Now I like to think of that being stored
in some kind of what I call an admin zone,
and I say that because we don't have direct access
to the raw storage of the Snapshot,
but we do know it's stored in S3.
What we have access to in the Amazon console,
we will see Snapshots as a resource that we have access to,
we just can't get to the underlying raw storage in S3.
AWS makes it really easy with the command line tools,
with the SDKs, even the console,
to copy that Snapshot to another region.
So for disaster recovery purposes,
we might want to create Snapshots here
and then perhaps our business policy
or some type of regulatory policy says
that we need geographical diversity in our data,
we can use this copy command to copy that Snapshot
to another region and perhaps we have our initial data
stored on the West Coast and we copy that
to a region on the East Coast and now we have
several thousand miles between our copies of data,
and that gives us our geographical diversity.
We can also share Snapshots between accounts.
If we're doing something with data in the production account
and we wanna get that back over to some kind of
development or test environment in another account,
we can do that as well,
we can share that Snapshot to another account.
The first time we take a Snapshot of an EBS volume,
we are going to take all of the data that's on that volume
and that will become our Snapshot.
From there on, subsequent Snapshots will be incremental,
that is, only new data or data that has changed,
you can see here that these blocks have changed,
and then of course we have another couple of blocks
that are new, new data, so only those blocks
that have changed or become new data
will be a part of that subsequent Snapshot.
So again, EBS Snapshots are the way to increase
the durability of your data to get geographical diversity
of your data and a way to recreate your volumes
in the case that they're lost or
accidentally deleted or whatever.
So that's EBS Snapshots within Amazon Web Services.