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Dell PowerFlex 4.5.x Technical Overview

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Storage virtual memory requirements

Table 1. Storage virtual memory (SVM) requirementsThis table describes the storage virtual memory requirements.
Component Memory allocation rules
Memory PowerFlex

RAM (GiB)

  • SDS FG: 10 GiB + 550 MiB per 1 TiB device size + 100 MiB per device
  • SDS MG: 5 GiB + 335 MiB per 1TiB device size
  • MD Read Cache: Total_Drive_Capacity_in_TiB * 8%
  • MDM: 6.5 GiB
  • CloudLink: 4 GiB
  • Operating System: 1 GiB
  • LIA: 0.35 GiB
  • PowerFlex Installer/PowerFlex Gateway: 8 GiB
  • SDC: 6 GiB
  • SDR: 8586 MiB + 550 MiB * (max remote PDs count)
    NOTE:SDR SVM support is only available as part of a PowerFlex appliance or the PowerFlex rack managed by PowerFlex Manager.
  • SDR memory requirement for hyperconverged systems (SVMs): 12GB
NOTE:For certain system configurations, the SDS needs to be configured to be able to use more than one non-uniform memory access (NUMA) domain. The SDS is configured by default to have affinity to socket 0 in a server or VM, and therefore, by default, the SDS is connected only to NUMA 0, and only has access to the memory in NUMA 0. If NUMA 0 (usually half the total memory) is less than the memory required by the SDS, you need to allow the SDS access to the memory in the other NUMA.

Non-Volatile RAM (NVDIMM):

  • Node storage capacity < 49 TiB: NVDIMM size 32 GiB
  • Node storage capacity 49 to 96 TiB: NVDIMM size 64 GiB
  • Node storage capacity > 96 TiB: NVDIMM size 96 GiB
NOTE:PowerFlex does not support using swap on Storage only and SVM nodes. This should be the default setting.

Using swap with PowerFlex has the following impact:

  1. Slows the performance of the system.
  2. Impacts I/O on the system disks which is used for swap. This may cause other functions that use the system disk to have slow I/Os such as:
    1. MDM repository related operations
    2. PowerFlex logs written to disk.
      Disable swap and set vm.overcommit to the following on nodes that have MDM and SDS process on them in the in/etc/sysctl.conf file: 
      vm.overcommit_memory=2
      vm.overcommit_ratio=100
Base SVM 350 MiB
Tiebreaker MDM 50 MiB

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