Welcome back and in the first
of this disaster recovery architecture series,
I want to make sure that you're comfortable
with the level of resilience
of various core product categories within AWS.
In this lesson, I'm covering storage,
and so by the end of the lesson,
I want you to be 100% sure on how an EC2 host
or Availability Zone or regional failure
can impact various different types of storage.
And by knowing that, you'll be able to answer questions
in the exam or deal with real-world situations
where components of the AWS regional
and global platform fail.
Now, I want to keep this brief
and it's going to be entirely visual,
so let's jump in and take a look.
Now, I'll be illustrating this with an architecture
that starts off with two regions,
us-east-1 and ap-southeast-2.
Now in there in blue,
is a cutdown list of Availability Zones in those regions
and then in green, across the bottom,
is anything which runs in the region,
but isn't AZ specific.
Now, there are a few things in this architecture
which can fail.
So we can have something within an Availability Zone,
a sub component of that Availability Zone
or just something that runs inside that Availability Zone.
We can also have the failure
of the Availability Zone itself.
We can have the failure of one of the regions
or we can have everything,
so both regions on this architecture.
Now, also with this architecture,
there are a few different types
of storage systems that we can use
and I want to cover how each of these can be impacted
by the failure of the infrastructure platform
at the various different levels.
Now, let's start with instant store volumes.
Instant store volumes are attached to a specific EC2 host,
an EC2 host which can also run EC2 instances.
Instant store volumes are one of the most high-risk forms
of storage available within AWS.
They have no resilience to failure of any kind.
If a physical storage device fails,
so one of the actual discs, then data is going to be lost.
And because they're attached to a host
which runs in an Availability Zone,
if the host fails or the Availability Zone fails,
then the instance store volumes
and the EC2 instances running on that host
in that Availability Zone, will also fail.
So there are multiple different ways
that failures can impact instant store volumes.
Hardware failure can impact it,
the failure of an EC2 host can impact it
and the failure of an Availability Zone
which that host runs in, can also cause failure.
Now, there's no way of preventing this.
That's why instant store is always viewed as temporary
and unreliable storage.
Luckily as solutions architects,
we also have elastic block store or EBS,
and this is a storage product which supports EC2.
It does this by allowing you to create volumes
which can be presented to EC2 instances.
Now, when you create a volume,
that volume is actually created
and runs within one Availability Zone.
Data is replicated in that one Availability Zone
between multiple underlying physical storage systems,
but the failure of an Availability Zone
will mean the failure of volumes
running within that Availability Zone.
There's no replication of data
from one Availability Zone to another.
And so if an Availability Zone fails, AZA in this case,
then all of the volumes within that Availability Zone
will also fail.
Now, you can't create an EBS volume
which runs across multiple Availability Zones
on multiple regions, it's just not possible.
One EBS volume runs from one Availability Zone.
Now, we also have the simple storage service known as S3
and any data which runs in S3, in most cases,
is replicated across multiple Availability Zones
within a single region.
Now, you can create a snapshot of an EBS volume
and store that in S3
and this means that the snapshot now benefits
from this increased level of resilience.
So now a snapshot would require an entire region to fail
in order for that snapshot to fail.
Now, you can't use snapshots directly.
You can't connect a snapshot to an EC2 instance.
Snapshots are read-only copies of data on a volume
at a given point in time.
S3 can be used to store objects as well,
so it's not only snapshots.
It's actually a great place for large media
or backups of any kind
which you need to be regionally resilient.
Now, it has different storage classes,
and one of these is known as One Zone
and with One Zone, it means it isn't regionally resilient,
because it's not replicated
outside one single Availability Zone.
But on the whole, most data that's stored in S3,
by default, will be replicated
across multiple Availability Zones.
Another storage service that we can use
as solutions architects, is the elastic file system
known as EFS.
Now, with this product, you create file systems
and one file system is replicated
across multiple different Availability Zones
within a single region.
An EFS file system can be mounted to Linux instances
and it means by default, this type of storage
can tolerate the failure of an Availability Zone.
It would actually require an entire region to fail
to impact an EFS file system.
Now, if you need even more resilience
to cope with bigger and bigger disaster events,
then you can look at a global level of recovery capability.
You could, for example, copy an S3 snapshot
between AWS regions.
And this means that even a region failure
wouldn't impact data,
because it's now stored in multiple locations globally.
With this snapshot copy that we've just created
in the ap-southeast-2 region,
you could then create a new EBS volume from it,
running in one AZ and attach this to an EC2 instance
also in one AZ, running on one single EC2 host.
It's important that you fully understand
all of this architecture.
You need to understand how much of the AWS global platform
would need to fail in order to affect data
that's stored on each one of these services.
For instance, store volumes, almost anything
can cause data loss.
It doesn't have any form of resilience.
For EBS, it could be impacted by the failure
of an Availability Zone.
For S3, an entire set of Availability Zones,
generally the entire region would need to fail
in order to impact data,
and the same is true for the elastic file system.
But you can even improve this further
by using S3 snapshot copy and copying data
to a new AWS region.
And as well as snapshot copy,
you've also got features like cross region replication,
which can copy normal S3 objects between AWS regions.
Now, why this is important, is that in the exam,
you're going to face questions
which ask you either how to recover for a given failure
or how to prevent a failure of a certain type
from causing data loss.
And using this visual, at least for storage,
you should now be able to answer
all of those type of questions.
For real-world solutions architects,
you're going to need to be able to design systems
which can meet customer demands
for certain levels of resilience,
and this will also help you to do that.
Now, that's it for this lesson
which covers the DR Architecture
and considerations for storage.
Thanks for watching.
Go ahead and complete this lesson and when you're ready,
I'll look forward to you joining me in the next.