Storage is a significant part of most IT budgets. As data volumes grow exponentially, new storage technology has evolved to accommodate it—including cloud-based storage, object storage, and distributed storage. Storage tiering is a strategy that lets you optimize the use of storage resources, efficiently backup data, save costs and make the best use of storage technology for each data class.
In this article you will learn:
- What is storage tiering?
- Advantages of tiered storage
- Cold storage vs hot storage
- The four-class tiered data model
- Tiered storage types: Tier 0-5
- What is automated storage tiering
- Storage tier best practices
- Bridging the hybrid cloud storage gap
This article is part of a series on Data Backup.
Read more in our articles on data archive and backup cloud storage.
What is Storage Tiering?
For example, SSD disk drives, magnetic disk drives and tape storage. The most important or frequently-accessed data is stored on the fastest, and most expensive media (SSD) and the least important on the slowest, cheapest media (tape).The minimal storage tiering system has two tiers—one for frequently accessed data and one for archive. The more tiers are available, the more choice administrators have over the placement of specific data classes, and the more efficiently storage resources can be utilized.
Storage tiering is not just about offering different storage technologies. A key aspect of a storage tiering architecture is how to classify data into levels of importance and assign it to the appropriate storage tiers. Over time, data classification can change—for example, as data ages, it may need to be moved into lower tiers or archive storage.
Data classification must be ongoing and must be smart enough to enable rapid classification of large volumes of data.
Advantages of Tiered Storage
Once you understand what is tiering, you can start leveraging this technique to optimize your storage. Some of the key advantages of tiered storage include:
- Reduced on-premises storage costs—storage tiering makes it possible to purchase less high-performance storage equipment and maintain an inventory or lower-performance, lower-cost storage devices.
- Reuse old equipment—storage tiering enables organizations to use older storage technologies which would otherwise be decommissioned, because they may still be suitable for lower-importance data classes or data intended for archiving.
- Reduced public cloud storage costs—on the public cloud, storage is billed by GB-month, so cost savings translate into a significant reduction in ongoing costs. Leveraging tiered storage on public cloud storage helps organizations pay less, while still providing users with the required level of access for each data class.
Cold Storage vs Hot Storage
A basic distinction in tiered storage is between “cold” and “hot” storage. The following table summarizes the differences between cold and hot data.
| Cold | Hot | |
| Required Access Speed | Slow | Fast |
| Access Frequency | Low | High |
| Value of Data | Low | High |
| Storage Media | Slower drives, tape | Faster drives, SSD |
| Storage Location | May be off-premises | Colocated or fast link to the data consumer |
| Cost | Low cost | High cost |
A Four-Class Tiered Data Model
The “hot vs. cold” model is useful but is not granular enough for many tiered storage systems. The following system of four data classes is more expressive:
- Mission-critical data—data required for high-performance applications, where delays can cause damage to the organization.
- Hot data—data in constant use by the business, performance is important but needs to be balanced with cost.
- Warm data—data that may be required by organizational users but is not in constant use. An example might be transactional data from the past week, which is occasionally consulted, viewed or used for reporting. Cost is the primary consideration for warm data, but it must provide reasonable access speeds.
- Cold data—data that is rarely or never accessed. It may only be maintained for regulatory reasons or may be kept because it might have value in the future. In other cases, cold data is maintained to facilitate big data analytics which is not performance-sensitive. Cold data is appropriate for the lowest cost storage tier available.
Tiered Storage Types: Tier 0, 1, 2, 3, 4, 5
While for some organizations a three tiered storage model is sufficient, many organizations maintain up to five tiers of storage equipment.
| Type | Storage Media | Used For |
| Tier 0 | Tier 0 includes SSD, RAM, PCIe Flash | You can use Tier 0 for high performance workloads. |
| Tier 1 | Tier 1 includes fast disks, all-flash storage, hybrid flash storage | You can use Tier 1 for mission-critical or highly sensitive files. |
| Tier 2/3 | Tier 2 and Tier 3 include Slow-spinning HDD, disk-based backup appliance, cloud storage, tape | You can use Tier 2 and Tier 3 for backups of mission critical data, which requires high reliability but not instant retrieval from backup. |
| Tier 4 | Tier 4 include SATA drives | You can use Tier 4 for warm data, data used for periodic reporting. |
| Tier 5 | Tier 5 includes tape storage, cloud storage archive tiers (e.g. Amazon Glacier) | You can use Tier 5 for cold data which is rarely or never accessed. |
What Is Automated Storage Tiering?
Automated storage enables you to optimize your storage tiering by adapting to your needs dynamically. It continuously monitors data use and access to determine the priority of data and what level of tiering is needed. To use automated storage, you configure your desired thresholds and leave the rest to automation.
Once data hits predefined thresholds of use it is moved accordingly. If the frequency of data access has increased, it is moved up to a lower-latency tier. If data is not being used, it is moved down to a lower-cost, higher-latency tier. In this way, your costs and performance are optimized with minimal effort and no ongoing maintenance.
Storage Tier Best Practices
When implementing storage tiers there are several best practices you can follow to further improve your cost savings and performance gains. Below are a few you can start with.
Don’t underestimate flash caching
Flash caching uses solid-state storage to hold only your most frequently accessed data. This offers significantly faster retrieval times than traditional drive storage. Traditionally, flash media has only been used for tier 1 storage. However, advances in technology and careful use can allow you to take advantage of flash storage with lower costs than was previously available.
To maximize flash caching, you can set up your system so that only your most important data ever gets transferred to the drive. This is done by setting short time parameters for how often data must be accessed before it is moved to the flash cache tier.
Use disk storage wisely
Disk storage is ideal for infrequently accessed data, such as backups or archives. It is resilient and high capacity but offers slower retrieval speeds. However, the bandwidth required for disk storage use, and the cost of the media can be a challenge. To reduce your costs, try to restrict disk storage to tier 2 or 3 data.
You can ensure that you get the best possible performance from your disk drives by using high RPM drives. Maximizing your available memory and using buffering can also help optimize your read/write operations.
Consider network performance
Network performance has a huge impact on the overall performance of your storage systems. No matter how fast or high capacity your storage tiers are, if you don’t have the network to support those tiers, your performance will suffer.
To prevent network-based bottle necks, make sure that your networks are capable of transferring the amounts of data you need at the speeds your tiers can provide. It’s also important to monitor your network traffic to detect and correct issues when one occurs. For example, if you have a scheduling conflict with backups.
Ideally, networks should be designed to handle the works case scenario—full backup recovery across multiple systems simultaneously. If your network can match the requirements of your full disaster recovery expectations, you should be good in normal situations.
Bridging the Hybrid Cloud Storage Gap with Cloudian
In the modern enterprise, storage tiering has a hybrid cloud angle. Whether data is stored on-premises or already in the cloud, the option of transferring it to cloud storage, or from the cloud to on-premise storage, is always on the table. To utilize storage options to the fullest in a cloud environment, you need granular control over data sets, with the ability to set different SLAs and policies for each data type and class.
Cloudian HyperStore gives you ultimate flexibility for moving data between warm and cold data tiers (tiers 3, 4, and 5). HyperStore offers a low-cost, cloud-scale on-premise storage option, letting you easily move local data to warm or cold storage. It also integrates with public cloud storage systems like Amazon S3/Glacier, Azure Blob Storage and Google Cloud Storage, letting you transfer data on demand to and from the cloud.
Learn more about Cloudian’s hybrid cloud storage solution, or learn more about using Cloudian to manage multi-cloud storage deployments.