Is Your Storage as Quick as a Flash? Part I
The term “flash” has been tossed about in the storage industry for years. It seems like everyone has a story around flash but NetApp approaches the flash technology in their storage systems a little differently from other storage vendors. From NetApp’s perspective, flash is all about storage efficiency. Instead of moving data between different tiers of storage and incurring the I/O penalty for doing so, NetApp relies on intelligent caching at the Controller, Array or even the Server side in what they refer to as the Virtual Storage Tier (VST). In this post I will discuss what the VST is, as well as its three technologies. In future posts I will dig into each of the technologies that make up the VST and discuss how they work and where to deploy them.
Whether it is a PCI-e flash card or a Solid-State disk (SSD), flash technology is relatively expensive compared to spinning disks. NetApp uses an intelligent caching layer known as the VST to make efficient use of the flash cards and SSDs. Only “hot” data is promoted to the cache. This intelligent use of cache not only reduces the overall capacity requirements for the cache itself but also reduces the processing burden on the system and traffic in the disk subsystem. Utilizing the VST can reduce the overall spindle count for a specific workload or even enable the use of capacity type, SATA drives, as the primary disk technology in a system.
The VST is integrated with the NetApp Unified Storage Architecture and fully compatible with SAN and NAS environments. Because of the tight integration, data deduplication and FlexClone efficiencies are preserved when data is promoted to the VST.
The three technologies that make up the VST are Flash Cache, Flash Pool and Flash Accel. Flash Cache is a PCI-e card, controller-based caching solution that is designed to improve performance for random read intensive workloads. Flash Pool combines hard drives and SSDs into a hybrid aggregate for array-based caching for both random read and write operations. Lastly, Flash Accel is a server-based software solution that leverages server side flash to cache random read operations of a virtual server infrastructure.
By making efficient use of the cache, NetApp enables customers to buy less cache and fewer disks, or even capacity-based disks rather than performance-based disks. These efficiencies mean that the storage system will use less power, cooling and space in the datacenter. Although NetApp promotes the benefits of efficiency, it is not a case of either efficiency or performance. The VST enables performance by making efficient use of system resources.
Please stay tuned in the coming weeks for new posts, where I will deep dive into Flash Cache, Flash Pool and Flash Accel.