VNX recommended system read/write cache values

The storage processor’s operating environment, features, installed apps and read/write cache use a shared memory called system memory. The amount of system memory depens on the VNX model.
The storage system’s memory is a resource that must be managed for best performance results. The capacity of the read/write cache, particularly the write cache, determines the system ability to smoothly handle bursts of write activity within a workload.

Maximum cache allocations VNX O/S Block 31.0 and File 7.0:

Per Storage Processor Memory VNX5100 VNX5300 VNX5500 VNX5700 VNX7500
Maximum (MB) 4000 8000 12000 18000 24000
Maximum Cache (MB) 801 3997 6988 10906 14250

Allocate 10% of available cache to read (with a minimum of 256 MB and a max of 1024 MB), and the rest to write.  Please note that certain Array features, such as FAST VP and Compression, will reduce the overall memory available for Read and Write cache, hence the minimum 256MB Read cache reference.  Setting read to 10% (with min and max) would lead to the following:

  • VNX5100 – Read 100 MB [Block-only system]
  • VNX5300 – Read 400 MB [Block & Unified]
  • VNX5500 – Read 700 MB [Block & Unified]
  • VNX5700 – Read 1024 MB [Block & Unified]
  • VNX7500 – Read 1024 MB [Block & Unified]
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