Tuesday, 16 August 2016

VCP6-DCV Exam Cram Notes: Section 3 of 10

Section 3 - Configure and Administer Advanced vSphere 6.x Storage

VMFS3 (datastore) creation is not supported in vSphere 6.x

Physical Raw Device Mapping - allows the virtual machine to have direct access to the LUN attached to it.

Objective 3.1 - Manage vSphere Storage Virtualization

List of Storage Adapters: SCSI, iSCSI, RAID, Fibre Channel, FCoE, Ethernet

Device drivers are part of the VMkernel and are accessed directly by ESXi.

SCSI INQUIRY Identifier: The host uses the SCSI INQUIRY command in order to use the page 83 information (Device Identification) to generate a unique identifier:
- naa.number
- t10.number
- eui.number

Path-based identifier (when device does not return page 83 information):
- mpx.path
e.g.: mpx.vmhba1.C0.T0.L0
Note: This is created for local devices during boot and is not unique or persistent.

Legacy Identifier:
- vml.number
The number digits are unique to the device and can be taken from a part of the page 83 information if available.

A hardware iSCSI adapter offloads the network and iSCSI processing from the host.
- Dependent Hardware iSCSI Adapter
-- Depend on VMware networking and iSCSI management interfaces within VMware
-- Depend upon host’s network configuration for IP and MAC
- Independent Hardware iSCSI Adapter
-- These types of adapters are independent from the host and VMware
-- Provides its own configuration management for address assignment
- Software iSCSI Adapter (built into VMware’s code; uses host resources)

Statements regarding iSCSI adapters...
... Dependent Hardware iSCSI adapters require VMkernel networking
... Independent Hardware iSCSI adapters do not require VMkernel networking

Virtual Disk Thin Provisioning:
- Allows you to create virtual disks of a logical size that initially differs from the physical space used on a datastore
- Can lead to over-provisioning of storage resources

Array Thin Provisioning:
- Thin provision a LUN at the array level
- Allows you to create a LUN on your array with a logical size that initially differs from the physical space allocated.
- Array thin provisioning is not ESXi aware without using the storage APIs for array integration (VAAI).
- Using VAAI you can monitor space on the thin provisioned LUNs, and tell the array when files are freed to reclaim free space.

Opinion: If your array supports array thin provisioning and VAAI then use array thin provisioning and thick disks within vSphere.

Zoning:
- Use single-initiator zoning or single-initiator single-target zoning
- Reduces the number of LUNs and targets presented to a particular host
- Controls/isolates paths in your SAN fabric
- Prevents unauthorized systems from accessing targets and LUNs

LUN masking:
- Limits which hosts can see which LUNs
- Can be done at the array layer or the VMware layer

Scan/Rescan storage:
- When adding a new storage device
- After adding/removing iSCSI targets

Rescan Storage actions:
- Scan for new Storage Devices
- Scan for new VMFS Volumes

Configure FC/iSCSI LUNs as ESXi boot devices:
- Each host must have access to their own boot LUN
- Individual ESXi hosts should not be able to see boot LUNs other than their own
- Check with vendor to configure storage adapter to boot from SAN
- iSCSI software adapter (or dependent adapter) can be used if it supports iBFT (iSCSI Boot Firmware Table)
- Configure boot sequence in BIOS

Create NFS share for use with vSphere:
- Create storage volume (and optional folder)
- Create an export for that volume (or folder) allowing IP of host(s) read/write access to the storage

4 different storage filters in vSphere 5 that are enabled by default:
- config.vpxd.filter.vmfsFilter
- config.vpxd.filter.rdmFilter
- config.vpxd.filter.SameHostAndTransportsFilter
- config.vpxd.filter.hostRescanFilter

Authentication methods for Outgoing and Incoming CHAP (iSCSI):
- None
- Use unidirectional CHAP if required by user
- Use unidirectional CHAP unless prohibited by target
- Use unidirectional CHAP
- Use bidirectional CHAP

Use case for Independent hardware iSCSI initiator:
- if you have a very heavy iSCSI environment with a lot of I/O (OLTP)

Use case for Dependent hardware iSCSI initiator:
- a high iSCSI I/O environment

Use case for Software iSCSI initiator:
- Low cost

Use case for array thin provisioning:
- Uniformity
- Less overhead
- ease of use

Objective 3.2 - Configure Software-defined Storage

Before you can configure Virtual SAN (VSAN):
- You need at least 3 hosts to form a VSAN cluster
- Each host requires minimum of 6 GB memory
- Make sure devices/firmware are listed in VMware Compatibility Guide
- Ensure you have the proper disks needed for the intended configuration (SAS and SSD, or just SSD)
- Storage device for VSAN must be local to ESXi host with no pre-existing partitions
- Each disk group will need one SAS drive and one SSD drive, or two SSD (one SSD is for caching)
- Ensure enough space to account for availability requirements
- The latest format 2.0 of VSAN requires 1% capacity per device
- In all flash configurations, untag the SSD devices that will be used for capacity

Note i: VSAN will never put more than one replica of the same object in the same fault domain.
Note ii: Can Enable/Disable Virtual SAN Fault Domains

Configure the VSAN network:
- VSAN doesn’t support multiple VMkernel adapters on the same subnet
- Multicast must be enabled on the physical switches
-- Allows metadata to be exchanged between the different hosts in a VSAN cluster
-- Enables the heartbeat connection between the hosts in the VSAN cluster
- Segment VSAN traffic on its own VLAN
- Use fault domains to spread data across multiple hosts
- Use 10 GbE adapter(s) on your physical hosts
- Create a port group on a virtual switch specifically for VSAN traffic
- Ensure the physical adapter used for VSAN is assigned as an active uplink on the port group
- Need a unique multicast address for each VSAN cluster on same layer 2 network

Note i: Virtual SAN is enabled (tick ‘Turn ON’) on the cluster
Note ii: Add disks to storage modes: Automatic or Manual
Note iii: Licensing for VSAN is required

Creating a VVOL (VMware Virtual Volume) - high level steps:
- Register Storage Providers for the Virtual Volumes*
- Create a Virtual Datastore**
- Verify that the protocol endpoints exist
- (Optional) Change the PSP for the protocol endpoint

*Usually VASA provider URL for the underlying storage array
**Select VVOL as the type of datastore

VM Storage Policies -> Create a new VM storage policy...
Note: Storage Policies can have tag-based rules
Note: If you see zero storage policies, you need to enable VM storage policies
Note: Options include: Compatible and Incompatible

Note: The Virtual SAN network - is used for HA Network Heartbeat configuration on a Virtual SAN cluster

Two virtual machine states indicative of a fault in the Virtual SAN cluster...
... The virtual machine is non-compliant and the compliance status of some of its objects is noncompliant
... The virtual machine object is inaccessible or orphaned

Objective 3.3 - Configure vSphere Storage Multi-pathing and Failover

Identify available Storage Load Balancing options - paths status:
- Active -- used for active I/O*
- Standby -- The path will become active if the active path fails
- Disabled -- this means the path is disabled and can’t accept data
- Dead -- this path currently has no connectivity to the datastore/device
*Active path currently accepting data will be marked “Active (I/O)”

Identify available Storage Multi-pathing policies:

- 2 types of multi-pathing policy available to storage devices:
-- PSP = Path Selection Policy
-- SATP = Storage Array Type Policy

- The 3 types of PSPs available through the Native Multipathing Plugin (NMP) are:
-- Round Robin (most common): selected I/Os are sent down different available paths at a set interval (default set interval is 1000)
-- Most Recently Used (MRU): sends all I/O down the first working path that is discovered at boot time. There is no failback after failover. This PSP is generally used for active/passive storage arrays.
-- Fixed: sends all I/O down the path that you set as the preferred path (or - if no path is set - first working path discovered at boot time.) There is failback.

Note: A SATP is the plugin that gets associated with the different paths to a device. Typically the SATP relates to the storage vendor or to the type of storage array that the device is connected to.

Identify features of Pluggable Storage Architecture (PSA):
- VMware NMP (Native Multi-Pathing Plugin)
- VMware SATP (VMware Storage Array Type Plugin)
- VMware PSP (Path Selection Policy plugin)
- Third-Party MPP (Multi-Pathing Plugin)
- Third-Party SATP (Storage Array Type Plugin)

Image: Pluggable Storage Architecture (PSA)

Some things the VMware NMP or Third-Party MPP are responsible for:
- Provides logical and physical path I/O statistics
- Loads and unloads Multipathing plugins
- Routes I/O requests for a specific logical device to the MPP managing that device
- Handles I/O queuing to the physical HBAs
- Handles physical path discovery and removal
- Implements logical device bandwidth sharing between virtual machines

Multi-Pathing modules provide the following:
- Manage physical path claiming and unclaiming
- Manage creation, registration and deregistration of logical devices
- Associate physical paths with logical devices
- Support path failure detection and remediation
- Process I/O requests to logical devices

Considerations for Storage Multipathing...
...  The default SATP for iSCSI or FC devices is VMW_SATP_DEFAULT_AA and the default PSP is VMW_PSP_FIXED
... If VMW_SATP_ALUA is assigned to a specific storage device, but the device is not ALUA-aware, performance could be degraded

Objective 3.4 - Perform Advanced VMFS and NFS Configurations and Upgrades

Identify VMFS5 capabilities:
- VMFS5 datastore capacity is 64TB
- Block size is standardized at 1MB
- Greater than 2TB storage devices for each VMFS5 extent
- Supports virtual machines with greater than 2TB disks
- Greater than 2TB Raw Device Mappings (RDMs)
- Support for small files (1KB)
- Ability to reclaim physical storage space on thin provisioned storage devices

Note: Any VMFS datastore you want to put in maintenance mode must be in a datastore cluster.
Note: Preferred path can only be set on a datastore that is using the Fixed Path selection policy.

NFS datastores support NFS v3 and NFS v4.1

Identify available Raw Device Mappings (RDM) solutions:
- RDMs come in two flavours, virtual compatibility mode and physical compatibility mode
- An RDM is a file that exists inside a VMFS volume which manages all the metadata for the raw device
- Some use cases for using RDMs:
-- Storage resource management software
-- SAN management agents
-- Replication software
-- Microsoft Failover Clustering
Note: Whenever software needs direct access to the SCSI device the RDM needs to be in physical compatibility mode.

To Disable VAAI: Host > Manage > Settings> Advanced System Settings
- HardwareAcceleratedMove = 0
- HardwareAcceleratedInit = 0
- HardwareAcceleratedLocking = 0
Note: To Enable VAAI set back to 1.

Use case for multiple VMFS/NFS Datastores:
- Datastores sit on backend storage that have physical disks configured in a particular way
- Disk contention could be a problem
- HA and resiliency

Objective 3.5 - Setup and Configure Storage I/O Control

Datastore Capabilities -> Edit -> Enable Storage I/O Control

Manage the method of which SIOC is implemented:
- Percentage of peak throughput
- Manual (based on milliseconds)
Note: Can choose to ‘Exclude I/O Statistics’ from SDRS

3 different graphs to monitor SIOC:
- Storage I/O Control Normalized Latency
- Storage I/O Control Aggregate IOPs
- Storage I/O Control Activity

Storage I/O Control will not function correctly if...
... Two different datastores share the same spindles

Miscellaneous

To create a 3TB VMDK on a 2TB VMFS5 datastore on an ESXi 6.x host, two possible actions...
... Increase the LUN on which the VMFS5 datastore resides to more than 3TB, and then grow the datastore to use the added capacity.
... Map a new LUN that is larger than 1TB to the ESXi host then add the new LUN as an extent to the VMFS5 datastore.

Two solutions to eliminate potential sources of SCSI reservation conflicts (which are causing slow performance)...
... Reduce the number of snapshots
... Upgrade the host to the latest BIOS

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