Azure Storage Account Hot, Cool & Archive Storage

Azure Storage Account Hot, Cool & Archive Storage

26 April 2018

Storage Account :-

An Azure storage account provides a unique namespace to store and access your Azure Storage data objects. All objects in a storage account are billed together as a group. By default, the data in your account is available only to you, the account owner.

Two types of storage accounts:

(i) General-purpose Storage Accounts ( V1 and V2)

Used for Azure Storage services such as Tables, Queues, Files, Blobs and Azure virtual machine disks under a single account.

(ii) Blob Storage Accounts

Blob storage account is a specialized storage account for storing your unstructured data as blobs (objects) in Azure Storage.

Blob storage accounts supports only block and append blobs, and not page blobs.

Storage account performance tiers.

All three type of storage account support below performance tiers
Two performance tiers * Performance tiers Cannot be changed once storage account created.

(i) Standard storage performance (default), backed by magnetic Drive , lowest cost per GB, good for the application which need bulk storage and data accessed infrequently.

(ii) Premium storage performance -backed by SSD, low-latency performance, at this moment only can be used for the Virtual machine Disk.

* Virtual machine with premium storage for all disk qualify for 99.9% SLA even when running outside of an availability set.

Storage account Access tiers

Storage account support two type of access tiers. Access tiers are only available for the General-purpose Storage Accounts V2 and Blob Storage Accounts

(i) Cool -> ideal for the infrequently accessed data.

(ii) Hot - (Default) -> ideal for the frequently accessed data

* there is another tier called archive but this is available at blob level , not at storage account level.

Storage account Replication

Storage account have three replication options: and LRS, ZRS , GRS & RA-GRS

(i) Locally-redundant storage (LRS) -

LRS guarantees that Microsoft will store 3 copies (replicas) of your data in a single datacenter.

provide at least 99.999999999% (11 9's) durability of objects over a given year

A write request to an LRS storage account returns successfully only after the data has been written to all replicas

each reside in separate fault domains and update domains within one storage scale unit.

LRS is the lowest cost replication option and offers the least durability

(ii) Zone-redundant storage (ZRS)-

ZRS guarantees that Microsoft will store 3 copies (replicas) in three storage clusters (2 to 3 facilities) in a single region.

ZRS provides excellent performance and extremely low latency

ZRS offers durability for storage objects of at least 99.9999999999% (12 9's) over a given year

ZRS currently supports standard, general-purpose v2 (GPv2) account types

ZRS may not protect your data against a regional disaster where multiple zones are permanently affected

ZRS currently only supports block blobs.

ZRS is generally available in the following regions

US East 2,US Central, North Europe, West Europe, France Central, Southeast Asia

(iii) Geo-redundant storage (GRS) & RA-GRS : Cross-regional replication for Azure Storage

GRS adds an additional 3 copies to a 2nd datacenter in a paired region and RA_GRS makes that second copy readable.

Geo-redundant storage (GRS) is designed to provide at least 99.99999999999999% (16 9's) durability of objects over a given year.

Data is durable even in the case of a complete regional outage or a disaster in which the primary region is not recoverable.

GRS replicates your data to another data center in a secondary region, but that data is available to be read only if Microsoft initiates a failover from the primary to secondary region

Read-access geo-redundant storage (RA-GRS) is based on GRS. RA-GRS replicates your data to another data center in a secondary region, and also provides you with the option to read from the secondary region.

For a storage account with GRS or RA-GRS enabled, all data is first replicated with locally-redundant storage (LRS). An update is first committed to the primary location and replicated using LRS. The update is then replicated asynchronously to the secondary region using GRS. When data is written to the secondary location, it is also replicated within that location using LRS

Since asynchronous replication involves a delay, changes that have not yet been replicated to the secondary region may be lost if data cannot be recovered from the primary region, for example in the event of a regional disaster.

When you enable read-only access to your data in the secondary region, your data is available on a secondary endpoint as well as on the primary endpoint for your storage account. The secondary endpoint is similar to the primary endpoint, but appends the suffix –secondary to the account name. For example, if your primary endpoint for the Blob service is myaccount.blob.core.windows.net, then your secondary endpoint is myaccount-secondary.blob.core.windows.net. The access keys for your storage account are the same for both the primary and secondary endpoints.

Prices for Hot storage start at $18.85 per TB for LRS.

Prices for Cool Storage start at $10.24 per TB for LRS.

Cool also has a data retrieval fee of $10.24 per TB that is free in the hot tier.

Finally, there is the fairly new archive storage. This is priced at an extremely low price of $2.048 per TB.

Converting between tiers is simple and can be performed using the Azure portal, Powershell or the Azure CLI, the conversion time can take up to 15 hours.

In the Gui, you simply select your blob (file) and choose the desired tier.

For full pricing details please see the Azure blob storage pricing site over here

The following table provides a quick overview of the scope of durability and availability that each replication strategy will provide you for a given type of event (or event of similar impact).

Scenario	LRS	ZRS	GRS	RA-GRS
Node unavailability within a data Center	Yes	Yes	Yes	Yes
An entire data Center (zonal or non-zonal) becomes unavailable	No	Yes	Yes	Yes
A region-wide outage	No	No	Yes	Yes
Read access to your data (in a remote, geo-replicated region) in the event of region-wide unavailability	No	No	No	Yes
Designed to provide _durability of objects over a given year	at least 99.999999999% (11 9's)	at least 99.9999999999% (12 9's)	at least 99.99999999999999% (16 9's)	at least 99.99999999999999% (16 9's)
Available in _ storage account types	GPv1, GPv2, Blob	GPv2	GPv1, GPv2, Blob	GPv1, GPv2, Blob

Comparison of the storage tiers

	Hot storage tier	Cool storage tier	Archive storage tier
Availability	99.90%	99%	N/A
Availability	99.99%	99.90%	N/A
(RA-GRS reads)
Usage charges	Higher storage costs, lower access and transaction costs	Lower storage costs, higher access and transaction costs	Lowest storage costs, highest access and transaction costs
Minimum object size	N/A	N/A	N/A
Minimum storage duration	N/A	30 days (GPv2 only)	180 days
Latency	milliseconds	milliseconds	< 15 hrs
(Time to first byte)
Scalability and performance targets	Same as general-purpose storage accounts	Same as general-purpose storage accounts	Same as general-purpose storage accounts