Home > Storage > PowerScale (Isilon) > Product Documentation > Storage (general) > PowerScale OneFS SmartFlash > L3 cache and Global Namespace Acceleration
Global Name Space Acceleration, or GNA, is a configurable component of the OneFS SmartPools data tiering product. GNA’s goal is to help accelerate metadata read operations (filename lookup, access, and so forth). It does so by keeping a copy of the metadata for the entire cluster on high-performance, low-latency SSD media. This increase the performance of certain workflows across the whole file system for legacy Isilon clusters where not every node contains SSD. To achieve this benefit, a mirror of all the metadata from storage pools that do not contain SSDs is stored on any SSDs available. As such, metadata read operations are accelerated even for data on node pools that have no SSDs.
To implement L3 cache and GNA in the same cluster, you must create path-based file pool policies that target an L3 cache enabled node pool. Set the data SSD strategy and snapshot SSD strategy for this L3 cache-enabled node pool to avoid SSD storage. This setting allows the L3 cache node-pool-to-reference metadata blocks in its L3 cache. It does not default to using the GNA metadata mirror on another pool, which would incur a latency penalty. To configure file pool policies, OneFS SmartPools must be licensed. The policies can be added by running the following command:
# isi filepool policies create <policy-name> --begin-filter --path <path> --end-filter --data-storage-target <L3-cache-node-pool-ID> --data-ssd-strategy avoid --snapshot-ssd-strategy avoid --apply-order 1
Note: The apply-order flag value 1, as shown in the preceding command example, puts this file pool policy at the top of the policy order.
To prevent capacity or performance oversubscription of a cluster’s SSD resources, several requirements must be satisfied in order to activate GNA on a mixed node cluster running L3 cache:
Assuming these requirements are met, you can enable GNA across the entire cluster through the OneFS WebUI by going to File System Management > SmartPools > Settings.
For workloads with a primary performance tier, and an archive element without SSD, you can run L3 cache and GNA in concert within the same cluster.
For example, in a cluster that has four PowerScale H700 nodes, four Isilon H400 nodes, and three Isilon NL400 nodes, you could:
Note: In the instances where all the nodes in the cluster contain SSD, L3 caching is intended as a replacement for GNA.