Storage Pool

What is a storage pool?

Storage pools are collections of storage volumes exported to a shared storage environment. Traditionally, storage pools were limited to storage volumes from a single vendor – for instance, you may have Flash and Disk storage volumes in a storage pool.

Storage pools may be homogeneous – that is, all the storage volumes are SSD/Flash, or all the storage volumes are disk, etc.  or they may be heterogeneous – the storage volumes are different classes of storage e.g. Flash, Disk, etc. Storage data tiering is an integral solution to handling heterogeneous storage pools.

What is storage tiering within a storage pool and why is it needed?

Storage tiering is a technique whereby the file metadata and the frequently-accessed blocks are stored in the highest tier and less-accessed blocks are downgraded to lower, cheaper tiers within a storage pool. This automated storage tiering approach allows the vendor to reduce costs by using smaller, faster tiers while still providing good performance. Storage tiering is often touted as a storage efficiency technique for customers to save on storage costs.  But a key thing to remember is that the bulk of the cost of data is not in the storage but in the active management and backups of the data.  Storage efficiency impacts the storage cost but not the active data management costs.

What is cloud tiering and how does it relate to storage pools?

Storage array vendors are now using their tiering technologies to tier data to the cloud. This is not what the technology was originally designed for, since the storage pool is no longer under a single vendor’s control and no longer local to a network.

Storage array vendors like NetApp and Dell EMC have created “Pool” solutions to externally tier data to less expensive storage such as in the cloud. Storage pools can reduce the cost of fast, expensive flash-based storage by migrating non-critical data sets to lower-cost storage for archiving and compliance and for “cold” data which hasn’t been accessed for a designated period of time to the cloud.

Read the blog post: What you need to know before jumping into the cloud tiering pool


What are the challenges and considerations for cloud storage pools?

While these solutions work well for tiering secondary data such as snapshot copies to the cloud, they result in unnecessary costs and lock-in when tiering and archiving files. As well, the pool approach tiers data in proprietary blocks versus files that all applications can understand. This presents the following challenges:

  • Policies to specify the blocks to be tiered are limited, resulting in much higher access rate to the cloud, and higher egress costs.
  • Block tiering to the cloud can reduce the performance of the storage array. Given the vast quantities of data most enterprises are dealing with today, block tiering is not suited for general data tiering to a public cloud across high latency channels.
  • Block tiering locks you into your storage vendor. Since the cold data is tiered to the cloud in a proprietary format, when it is time to decommission your storage array and replace it with a new one you must stay with the same vendor.
  • Proprietary lock-in. You cannot directly use native cloud services to access your data in the cloud. It has to be through the proprietary storage filesystem itself. This creates unnecessary licensing costs that customers must pay forever to access their data., resulting in much higher access rate to the cloud, and higher egress costs.

Download the white paper: Cloud Tiering: Storage-Based vs Gateways vs File-Based: Which is Better and Why?

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