There are a lot of
components that make Azure tick and storage is a big one. Azure has four types of storage - blobs,
files (in preview), table and queue.
Every storage account you create in your subscription has the ability to
contain all four types. In addition to
those types, you can pick from four redundancy options:
- Locally Redundant Storage
(LRS)
- Zone Redundant Storage (ZRS)
- Geographically Redundant
Storage (GRS)
- Read-Access Geographically
Redundant Storage (RA-GRS)
Locally Redundant
Storage (LRS) is the cheapest storage
option you can select and the end result will be three synchronous copies of
your data within a single datacenter.
The SLA offered is 99.9% availability for read and write functions. LRS is a good choice for data if you have
compliance requirement that dictates your data remain in a specific location.
Geographically
Redundant Storage (GRS) is the big brother of LRS. Data is copied three times within a single
datacenter, plus multiple asynchronous copies to a second datacenter hundreds
of miles away. This results in six
copies of your data. By default when you
create a storage account, it will be GRS.
You can see what secondary location would be used for your redundant
copy in the configuration settings of your storage account. The alternative copy provides protection
against a major datacenter outage or disaster, however you don't have control as
to when the secondary copy is made available for access.
Read-Access
Geographically Redundant Storage (RA-GRS) is the cool twin of GRS. It’s the same as GRS, but you have the
ability to access the secondary datacenter copy for read access whenever you
like. When you activate RA-GRS, you'll
be given a second endpoint URL for access to that copy. Because if this, the
SLA for read functions increases to 99.99%.
If you create a
storage account with any of the three choices above, you can easily change it
after the fact within the storage configuration settings.
Finally, there is
Zone Redundant Storage (ZRS). Similar to
LRS, but the three copies of data are stored across multiple datacenters within
or across regions. It's more durable than
LRS and more economical than GRS, but is an option for block blobs only. There
is no option to change from ZRS storage to the other options and you will see a
warning that ZRS if for blob storage only.
Block blobs are used for VM storage as well as documents, videos,
backups - any unstructured text or binary data - but you can't use the same storage account
for table or queue storage. Still this a
great option if you are looking for a little extra durability due to outage,
but don't need the full on redundancy offered by GRS or RA-GRS. Storage accounts used for testing purposes
would be good use of ZRS.
In addition to these
regular "spinning disk" storage options, you can also try out Azure
Premium Storage (in Preview). Premium Storage gives you high-performance,
low-latency support for I/O workloads running on Azure VMs. These persistent disks are backed by
SSD. However, you need to have a premium
storage account which can only be created using the Preview Portal and it's
currently only in limited regions.
Learn
more about Premium Storage here.
If you need to know
more about the specific pricing for Azure Storage you can visit the
pricing page.
Your total cost will depend on several factors, not just the redundancy option
you pick. As you look at the hybrid
cloud scenarios for storage, you'll find that the cloud won't be the best
location for ALL your data, but storing some data in the cloud can be cheaper
than expanding storage devices you already own.
Also, if you missed yesterday's series post on Azure Backup Solutions,
check it at
http://aka.ms/HybridCloudforITPro.
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