Archive for November 14, 2012

Identify and tag SSD devices

vSphere 5.0 or later can identify and tag SSD devices and use them as Host Cache. According to vSphere Resource Management guide, Host Cache will be used as Write Back Cache when VM memory needs to use vswp file. So if I understand this correctly Host Cache will help when VM needs to swap OUT to vswp file but when VM needs to read swapped page (swap IN) it still needs to read from vswp file.

You can use PSA SATP claim rules to tag SSD devices that are not detected automatically.
Only devices that are consumed by the PSA Native Multipathing (NMP) plugin can be tagged.

In my demonstration I have VMFS-02 that is identified as Non-SSD. Well this is not SSD based LUN so it is correctly detected, but using SSD tagging feature I can fool ESXi to believe this LUN as SSD.

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Understand and apply LUN masking using PSA-related commands

ESXi Server comes with several native PSA (Pluggable Storage Architecture) to perform certain storage related tasks.

I will go though LUN Masking at ESXi server in this blog. Usually LUN Masking is configured at SAN device to hide LUNs from hosts (HBAs) but ESXi allows you to hide LUNs to be displayed although LUN(s) are not masked by SAN device.

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Configure vCenter Server storage filters

vCenter Server applies storage filters to prevent undesirable LUNs to be displayed during the storage operation. For example if a LUN is used for RDM, a LUN will not be displayed in the list of available LUNs when you try creating a new VMFS Datastore. I cannot find or think about any use case of disabling these features but it can be tested in VCAP exam.

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VCAP5-DCA Objective 1.1 – Implement and Manage Complex Storage Solutions – Skills and Abilities

  • Determine use cases for and configure VMware DirectPath I/O
  • Determine requirements for and configure NPIV
  • Determine appropriate RAID level for various Virtual Machine workloads
  • Apply VMware storage best practices
  • Understand use cases for Raw Device Mapping
  • Configure vCenter Server storage filters
  • Understand and apply VMFS re-signaturing
  • Understand and apply LUN masking using PSA-related commands
  • Analyze I/O workloads to determine storage performance requirements
  • Identify and tag SSD devices
  • Administer hardware acceleration for VAAI
  • Configure and administer profile-based storage
  • Prepare storage for maintenance
  • Upgrade VMware storage infrastructure    Send article as PDF   

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