Acceleration Pools; Fault Sets - Dell EMC VxFlex Ready Node User Manual
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Acceleration Pools
Fault Sets
ensures that reading from a volume will not return information that was previously
deleted from the volume.
This behavior incurs some performance overhead on the first write to every area
of the volume since the area needs to be filled with zeros first.
FG is always zero padded.
Zero-padding disabled (default only for MG)
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A read from an area previously not written to will return unknown content. This
content might change on subsequent reads.
Zero padding must be enabled if you plan to use any other application that assumes
that when reading from areas not written to before, the storage will return zeros or
consistent data.
You can add Storage Pools during installation. In addition, you can modify Storage
Pools post-installation with most of the management clients.
Note:
The zero padding policy cannot be changed after the addition of the first
device to a specific Storage Pool.
Acceleration Pools enable RFCache of SSD or NVMe devices to accelerate an HDD
storage pool. It also enables NVRAM required for Fine Granularity (FG) storage pools.
RFCache Acceleration Pools features and requirements:
RFCache feature consumes the entire device, which prevents other features being
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used
You can only have a single RFCache Acceleration Pool per Protection Domain
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NDU creates a default RFCache Acceleration Pool
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You can disable/enable RFCache via PD, SP, and SDS
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A storage device benefits from RFCache acceleration if RFCache is enabled on all
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three levels and if the SDS actually contains RFCache devices
NVRAM Acceleration Pools features and requirements:
Must reside on NVDIMM devices
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The NVDIMM must be mapped to a DAX Device
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NVRAM Acceleration Pools cannot be disabled
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Migration to a different NVRAM pool is not supported
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Limitation: NVDIMM failure on SDS node causes failure of all node's SSDs in the FG
storage pool.
A Fault Set defines a group of SDSs that are more inclined to go offline
simultaneously. Defining a Fault Set configures VxFlex OS to mirror the devices in the
set.
A Fault Set is a logical entity that contains a group of SDSs within a Protection
Domain, that have a higher chance of going offline together, such as a group of SDSs
that are all powered in the same rack. By grouping them into a Fault Set, you are
configuring VxFlex OS to mirror the data for all devices in this Fault Set. The mirroring
should take place on SDSs that are outside of this Fault Set.
Dell EMC VxFlex Ready Node AMS User Guide
Architecture
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