Esxi Vstorage Apis For Array Integration (Vaai) - Dell EMC VxFlex Ready Node User Manual
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Fine Granularity layout checksum implementation
ESXi vStorage APIs for Array Integration (VAAI)
Pools with Fine Granularity with or without compression, have persistent
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checksum by default. This can't be changed.
Each I/O goes through compression, checksum is calculated before it is written to
the disk. There are two types of checksum:
Fine Granularity layout saves checksum data before and after processing to
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guarantee data integrity (compressed or not)
There are also system checksums for metadata
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This feature applies to all I/Os: Application, Rebuild, Rebalance, and Migrate. The
checksum is also kept in RMcache (Read Memory Cache), protecting every block that
is maintained in SDS memory against memory corruption. The checksum feature can
be enabled at the Protection Domain level, and defined at the Storage Pool level. The
feature is T10/DIF-ready.
The Fine Granularity data layout has a default checksum whether it is compressed or
not.
ESX vStorage APIs for Array Integration (VAAI) is a feature introduced in ESXi/ESX
4.1 that provides hardware acceleration functionality. It allows the host to offload
specific virtual machine and storage management operations to compliant storage
hardware. With the storage hardware's assistance, the host performs these
operations faster, and consumes less CPU, memory, and storage fabric bandwidth.
VAAI uses these fundamental operations:
Atomic Test & Set (ATS), which is used during creation and locking of files on the
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VMFS volume
Clone Blocks/Full Copy/XCOPY, which is used to copy or migrate data within the
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same physical array
Zero Blocks/Write Same, which is used to zero-out disk regions
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Thin Provisioning in ESXi 5.x and later hosts, which allows the ESXi host to tell the
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array when the space previously occupied by a virtual machine (whether it is
deleted or migrated to another datastore) can be reclaimed on thin provisioned
LUNs.
Block Delete in ESXi 5.x and later hosts, which allows for space to be reclaimed
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using the SCSI UNMAP feature.
The VxFlex OS supported VAAI features are:
Atomic Test & Set (ATS)
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Zero Blocks/Write Same
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Thin Provisioning in ESXi 5.x and later hosts
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Block Delete in ESXi 5.x and later hosts
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The following output is an example of typical output:
esxcli storage core device vaai status get -d
eui.7dbf14034834bbe01bf7e55800000002
eui.7dbf14034834bbe01bf7e55800000002
VAAI Plugin Name:
ATS Status: supported
Dell EMC VxFlex Ready Node AMS User Guide
Architecture
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