Instructor: So while we're on the subject,

let's talk about redundancy in Azure storage accounts.

So I'm in the process

of creating a storage account in east US.

When I get to the redundancy part of that basic screen,

I'm given four options locally-redundant storage,

geo-redundant storage, zone-redundant storage,

and geo-zone redundant storage.

What does this all mean?

So the concept of redundancy is that by default for free,

Microsoft is going to keep multiple copies of my files

in case of failure in case of emergency.

So even at locally redundant storage, which is the cheapest

and most basic option, Microsoft is gonna keep a total

of three copies of any file I upload

into the storage account.

So the reason it does that is

because hard drives from time to time fail,

they are spinning magnetic discs.

And despite our best efforts in engineering,

after so many thousands of hours of active use,

the hard drive could experience some type of failure.

So Microsoft keeps two additional copies of that file

such that if the hard disk was to fail,

then they're able to reconstruct the hard disc

based on the files they already have stored elsewhere.

The reason they do three

and not two is in the very, very unlikely case

that two hard drives fail, that contain the same files.

So this is giving you a lot of redundancy

and resistance to failures, server rack

and drive failures.

So for locally redundant storage,

you're going to get three copies of your files.

This is stored in a data center.

So I've chosen east US as my region.

This is gonna be stored in one region

of the east US region in one data center.

Now zone-redundant storage would be the next more redundant,

the safer option.

What this does, it still keeps three copies of my files,

but instead of keeping them in the same building,

it spreads them across three different buildings

in the region.

So these are called data centers.

And so zone-redundant storage would protect you in case

that the entire building was to lose power

or to have a flood or some kind of a disaster was to strike.

Your files are safely stored

in a physical separate location.

I should point out that not every

option is available in every region.

So in east US it has these options.

If I go down to north central US,

it's one of the older regions

and we can see that there's only locally-redundant

and geo-redundant.

It doesn't have the concept of zones in north central US.

So as you might expect,

then going to geo-redundant storage is even safer still.

This takes your data out to another region.

So in the case of east US, this could store three copies

of your data in a single data center in east US,

as well as three copies

of your data in a single data center in west US.

So these regions are paired

and so they're basically storing six copies

of your files in two different regions.

Now, geo-redundant storage is also not available

in every region.

So for instance, if you go to Qatar,

then you'll see that you only have the option for locally

and zone-redundant storage.

And then for the last one, geo-zone redundant storage.

That is the safest option of all.

It's going to combine the two.

It's gonna keep three copies

of your files in three different data centers in a region

and three additional copies

of your files in three data centers in the other region.

There are costs associated with this.

So when we go to the costing screen, we can see,

I'll go back to east US.

That LRS is costing in that range

of 2.10 cents per gigabyte.

But if I go to a zone-redundant storage,

that is now 2.60 cents per gigabyte.

And I want to go to geo-redundant storage

prices could change of course, but 4.6 gigabytes.

You see we've now doubled the cost

and geo-zone redundant storage.

The last thing I would say about storage is when you get

into the geo-redundant storage area,

when you've got two regions,

you have the additional checkbox that allows you

to have a read-only access to the second region.

So if I was to check this checkbox,

I would have a second URL

that I could read data from the storage account.

So in the case of east US,

I know that the data's also stored in west US

and I would have a read-only URL

for the west US data in case of emergency.

And of course that does have an impact on pricing too.

So when I go to read access geo-redundant storage,

then I'm going up to 5.90 cents per gigabyte.

I believe it was 4.6 without that second option.

So an extra one

and a half cents almost for this option.

So redundancy really just makes it much more difficult

for Microsoft to lose your files.

The higher you up you go, the more you pay.

But then the more you would expect your files

to be perfectly fine

and survive for millions of years in Microsoft Azure,

as long as you pay for it.