Chapter 2: Storage Infrastructure Flashcards
How do virtual machines communicate with their virtual disks?
Using SCSI commands. These SCSI commands can also be encapsulated into other forms.
Describe the function of storage virtualization.
Storage virtualization refers to a logical abstraction of physical storage resources and capacities from virtual machines.
What kind of storage virtualization does ESXi provide?
ESXi provides host-level storage virtualization.
Describe a storage device / LUN.
Storage devices or LUNs are storage volumes that are presented to a host from a block storage system and are available to ESXi for formatting.
From the standpoint of a virtual machine, what does each virtual disk appear as?
Each virtual disk appears as if it were a SCSI drive connected to a SCSI controller.
What is the purpose of SCSI in regards to Fibre Channel (FC)?
Fibre Channel is a network storage protocol used on SANs. SCSI commands are encapsulated into Fibre Channel frames and used to direct storage.
What is the purpose of iSCSI?
Internet SCSI (iSCSI), is a SAN transport protocol that can use regular ethernet connections between ESXi hosts and storage systems.
What network components are required on ESXi hosts connect to a network using iSCSI?
Hosts will use hardware iSCSI adapters or software-based iSCSI initiators with regular network adapters.
What versions of NFS are supported by ESXi?
ESXi supports NFS versions 3 and 4.1.
In ESXi, when a datastore is deployed onto block storage devices, what file system is used?
Virtual Machine File System (VMFS).
What function of ESXi describes the following?
“A mapping file that contains metadata that resides in a VMFS datastore and acts as a proxy for a physical storage device”
A Raw Device Mapping (RDM).
What is the benefit of using a Raw Device Mapping (RDM)?
It allows for virtual machines to directly access physical storage.
When using Raw Device Mappings (RDM), how do virtual machines interact with their storage?
The VM configuration references the RDM, not the storage device. The RDM acts as a proxy between the VM and the physical storage.
What compatibility modes are supported by RDM?
There are 2 compatibility modes supported by RDM:
- Virtual compatibility mode: the RDM acts like a virtual disk file
- Physical compatibility mode: the RDM offers direct access to the SCSI device
What are the benefits of using virtual compatibility mode with RDMs?
Virtual compatibility mode allows for the same extra features that you would find with a regular virtual disk file. This includes virtual machine snapshots and the use of disk modes.
What are the benefits of using physical compatibility mode with RDMs?
Physical compatibility mode allows for more direct access to the SCSI device. This allows support for applications that require lower-level control.
Why would someone choose to use RDMs over regular virtual disks?
An administrator plans to use storage features that are inherent to the SAN itself such as:
- SAN management
- storage-based snapshots
- storage-based replication
Or for implementing Microsoft Cluster Server (MSCS)
What is the purpose of a vSAN?
By running a layer of distributed layer of software across hosts in a cluster, a vSAN can utilize local storage on each host as a single storage pool. This allows features that would normally be exclusive to dedicated shared storage.
Describe virtual volumes (vVols).
Virtual volumes are encapsulations of VM files, virtual disks, and their derivatives that are stored natively inside a storage system.
How are Virtual Volumes created?
Virtual volumes are not created manually. They are created automatically when you create, clone, or snapshot a VM.
How are are Virtual Volumes (vVols) different from regular storage management?
Regular storage management involves managing space from within datastores, vVols involve managing abstract storage objects that are handled by storage arrays. With vVols, each VM itself is a unit of storage management which can have storage policies applied to it rather than on the LUN or datastore.
What term describes the following?
“A framework that provides a single control panel across various data services and storage solutions.”
Storage Policy Based Management (SPBM).
What term describes the following?
“Software components that can be installed on ESXi hosts and can offer additional data services to virtual machines.”
I/O Filters.
Storage services such as replication, encryption, and caching are examples of what?
I/O Filters.
VMFS datastores can be created on what 4 types of storage devices?
Fiber Channel, iSCSI, FCoE, and local storage devices.
What versions of VMFS are supported by ESXi 7.0?
VMFS versions 5 & 6 for reading and writing.
A spanned VMFS datastore can support what types of homogenous storage devices?
512n, 512e, or 4Kn.
What is the block size that is supported by VMFS versions 5 & 6?
VMFS versions 5 & 6 support a 1 MB block size.
What is the purpose of a block size on a VMFS datastore?
The block size defines the maximum file size and amount of space a file occupies.
What types of datastores are supported for Storage vMotion?
Storage vMotion supports migration across VMFS, vSAN, and vVol datastores.
What partition type(s) are supported by VMFS version 5 & 6?
VMFS datastores support GUID Partition Table (GPT),
When a VMFS datastore is upgraded from version 3 to version 5, when does the conversion from an MBR, to a GPT partition take place.
Only once the partition grows beyond 2 TB. If the partition stays bellow this size, then it will remain as a Master Boot Record (MBR) type.
What security mechanisms are supported by NFS version 3 & 4.1?
NFS version 3 supports AUTH_SYS, version 4.1 supports AUTH_SYS and Kerberos authentication.
What encryption algorithms are supported by NFS version 4.1?
AES256-CTS-HMAC-SHA1-96 & AES128-CTS-HMAC-SHA1-96.
Which version(s) of NFS support multipathing?
Only version 4.1 of NFS supports multipathing through session trunking.
What locking mechanisms are supported by NFS versions 3 & 4.1?
NFS version 3 supports proprietary client-side locking, whereas version 4.1 supports server-side locking.
What features are supported by the version 3 of NFS, but not supported by NFS version 4.1?
The older version of NFS supports the following:
- Storage DRS
- Storage I/O Control
- Site Recovery Manager
How can datastores can converted from NFS version 3 to NFS version 4.1?
There are 2 main ways that a datastore can be migrated:
- Storage vMotion can be used to migrate virtual machines from NFS version 3 datastores to NFS version 4.1 datastores.
- In some cases, the NFS datastore can be unmounted and remounted as NFS version 4.1.
What type of datastore is created and manipulated out of band by a vSphere APIs for Storage Awareness Provider (VASA)?
vVol datastores.
Describe the function of VASA providers in regards to vVol datastores.
They map virtual disk objects and their derivatives directly to the VM on the storage system. These objects can include:
- Clones
- Snapshots
- Replicas
How do ESXi hosts access virtual volumes (vVols)?
Through an intermediate point in the data path called the protocol endpoint.
What function do protocol endpoints serve in regards to storage?
Protocol endpoints serve as gateways for I/O between ESXi hosts and the storage system.
What network storage protocols are supported by protocol endpoints?
Protocol endpoints support Fibre Channel, FCoE, iSCSI, or NFS.
What 3 types of virtual disks are supported by vSphere with Kubernetes?
Ephemeral, container images, and persistent volumes.
A vSphere pod requires ephemeral storage to support what types of Kubernetes objects?
Logs, emptyDir volumes, and ConfigMaps.
Why does Kubernetes require persistent storage?
Some Kubernetes workloads require persistent storage to store independently of the pod.
What is the purpose of a First Class Disk (FCD)?
To store persistent volume objects in vSphere with Kubernetes.
What term describes using an indirect means to connect NVMe storage to a host?
Fabric Transport (NVMe-oF).
What NVMe term is analogous to a storage device (LUN) in other storage arrays?
An NVMe namespace represents a storage volume.
Describe the requirements for NVMe over RDMA (RoCE Version 2).
NVME over RDMA supports the following:
- An NVMe storage array with NVMe over RDMA transport support
- A compatible ESXi host
- Ethernet switches supporting a lossless network
- A network adapter that supports RDMA over Converged Ethernet
- A software NVMe over RDMA adapter
- An NVMe controller
Describe the requirements for NVMe over Fibre Channel.
NVME over Fibre Channel requires the following:
- A Fibre Channel storage array that supports NVMe
- A compatible ESXi host
- A hardware NVMe adapter (a Fibre Channel HBA supporting NVMe)
- An NVMe controller
Describe the purpose of the High-Performance Plug-in (HPP)?
HPP is used to improve the performance of NVMe devices on an ESXi host.
In ESXi, how are NVMe-oF targets presented to users?
As iSCSI targets.
What is the default plug-in for local NVMe devices?
VMware Native Multipathing Plug-In (NMP).
What is the recommended Plug-In to use with NVMe-oF?
VMware High-Performance Plug-In.
Describe the the path selection schemes (PSS) used by HPP when selecting physical paths for I/O requests.
HPP Path Selection Schemes:
- FIXED: A static/designated path
- LB-RR: Using the round-robin algorithm
- LB-IOPS: path selected by the least number of outstanding I/Os
- LB-BYTES: path selected by the least number of outstanding bytes
- LB-Latency: path selected by considering the latency evaluation time and the sampling I/Os per path
Describe the differences between a Hybrid and All-Flash vSAN cluster.
Hybrid clusters use flash devices for the cache layer, while relying on magnetic disks for the storage capacity layer. All flash clusters use flash storage for both cache and storage capacity layers.
Hosts contributing their local storage to a vSAN are also required to contribute ___?
At least one device for cache.
Describe the function of a disk group in vSANs.
The drives contributed by a host in a vSAN cluster form one or more disk groups. Each of these disk groups contains a flash cache device and at least one capacity device.
What term describes the following?
“A vSAN characteristic that provides highly scalable management of snapshots and clones”
On-disk format.
Describe the function of a fault domain.
Fault domains are configured to protect against rack or chassis failures by preventing all copies of VM disk data from residing on the single rack or chassis.
Describe the function of Data at rest encryption.
This function of vSANs provides encryption of data that is not currently in transit and on which no processes are being done. When a drive is removed, the data is encrypted.
In regards to vSAN objects and components, describe the function of the VM home namespace.
The VM home directory where all the VM files are stored.
In regards to vSAN objects and components, describe the function of the VM swap object.
Used during high periods of contention to allow memory to be swapped to disk.
What vSAN term describes the following?
“A change file created when a snapshot is taken of a VM.”
A snapshot delta VMDK.
What vSAN term describes the following?
“An object created when a VM is snapshotted and the VM’s memory is retained or suspended”
A memory object.
Describe the component states available of a vSAN component.
2 component states are available:
- Degraded: a permanent failure of a component
- Absent: a temporary failure of a component
Describe the object states available for a vSAN object.
vSAN has 2 object states:
- Healthy: At least one RAID mirror is available, or enough segments for RAID 5 or 6
- Unhealthy: No full mirror is available, or not enough segments for a RAID 5 or 6
How much space is consumed by metadata on a vSAN datastore when on-disk format version 1.0 is being used?
Version 1.0 consumes approximately 2 MB of space.
How much space is consumed by metadata on a vSAN datastore when on-disk format version 2.0 is being used?
Version 2.0 consumes approximately 4 MB of space.
What is the purpose of the Ruby vSphere Console (RVC)?
The RVC is the CLI interface used for managing the vSAN cluster, it comes installed with the VCSA deployment.
Describe the function of the vSAN Observer.
A web-based utility used for performance analysis and monitoring.
What term describes the following?
“The preconfigured deployment that is provided by VMware partners. It is a validated design using certified hardware.”
vSAN Ready Node.
What is the maximum disk capacity supported in vSAN 7.0?
A single physical disk of up to 32 TB is supported.
When deduplication and compression are enabled, what is the maximum logical capacity supported by vSAN 7.0?
Up to 1 PB.
What is the default storage platform for vSphere with Kubernetes?
Cloud Native Storage.
What is indicated by the PFTT number and what possible values are supported?
The Primary Level of Failures to Tolerate (PFTT) defines the number of site failures that a virtual machine object can tolerate. For a stretched cluster, only a value of 0 or 1 is supported.
What is indicated by the SFTT number and what possible values are supported?
The Secondary Level of Failures to Tolerate (SFTT) defines the number of additional host failures that an object can tolerate after the number of site failures (PFTT) is reached. The default value is 0, and the maximum value is 3.
What is the purpose and default value of Data Locality?
Data Locality enables you to restrict virtual machine objects to a selected site in the stretched cluster. The default value is None, but it can be changed to primary or secondary.
Data Locality is only available if the PFTT is set to _?
Zero.
DRS must be enabled on what type of vSAN cluster?
DRS must be enabled on a stretched vSAN cluster.
What are the 4 vSAN space efficiency techniques?
1) Thin provisioning
2) Deduplication
3) Compression
4) Erasure coding
How does deduplication increase storage efficiency?
Deduplication reduces duplicated data blocks by using SHA-1 hashes for data blocks.
What compression mechanism is used with vSAN?
LZ4, a lightweight compression mechanism.
What is the purpose of erasure coding?
To create a strip of data blocks with a parity block similar to RAID configurations. Except, erasure coding spans storage across ESXi hosts in the cluster rather than within the disks in the host.
What is the purpose of SCSI UNMAP commands?
SCSI UNMAP commands enable you to reclaim storage space that is mapped to deleted vSAN objects.
Which version of vSAN supports SCSI UNMAP commands?
vSAN version 6.7 Update 1 and later.
What types are unmaps are supported by vSAN?
Inline and offline.
On Linux, what commands are used to provide offline and inline unmaps?
Linux uses the following commands:
- Offline: fstrim(8)
- Inline: mount -o discard
Describe the difference between deduplication and compression in regards to vSAN.
Deduplication removes redundant data blocks, while compression removes additional redundant data within each data block.
Describe the function of RAID 5/6 Erasure Coding.
RAID 5 / RAID 6 Erasure Coding protects against data loss while increasing storage efficiency when compared with RAID 1.
What feature of vSAN best describes the following?
“A server used to provide vCenter with encryption keys”
A Key Management Server (KMS).
What does a VCSA store when it requests an AES-256 encryption key (KEK) from the KMS.
vCenter Server only stores the ID of the KEK (not the key itself).
What method of encryption is used by an ESXi host to encrypt disk data on a vSAN.
AES-245 in XTS mode.
What is the purpose of vSAN File Services.
vSAN File Services provides vSAN-backed file shares that virtual machines can access as NFS version 3 and 4.1.
What formula is used to plan capacity for a vSAN datastore using RAID 1?
Capacity = Expected Consumption Size x (PFTT +1).
How much capacity overhead is required by versions 1.0, 2.0, and 3.0 for vSAN?
Version 1.0: 1 GB per capacity device
Version 2.0: Up to 2% per capacity device
Version 3.0: 6.2% per capacity device
How much memory should be configured per host for full vSAN operations?
32 GB of memory.
What is the minimum amount of Fault Domains required to support a PFTT of 1?
At least 3 fault domains:
PFTT = n
Minimum = 2 x n + 1
In this instance:
PFTT = 1
Minimum = 2 x 1 + 1 = 3
What is the formula for calculating the memory vSAN Footprint?
vSANFootprinter = HOST_FOOTPRINT + NumDiskGroups x DiskGroupFootprint
What is the formula for calculating the memory Disk Group Footprint?
DiskGroupFootprint = DISKGROUP_FIXED_FOOTPRINT + DISKGROUP_SCALABLE_FOOTPRINT + CacheSize x CACHE_DISK_FOOTPRINT + NumCapacityDisks x CAPACITY_DISK_FOOTPRINT.
What version of ESXi do hosts need to be running to utilize full vSAN capabilities?
Version 6.7 Update 3 or later.
What are the host bandwidth requirements for an all-flash and hybrid vSAN configuration?
All flash: 10 Gbps, Hybrid: 1 Gbps.
What is the network latency requirements for the following vSAN areas?
- The RTT between member hosts in a standard vSAN cluster
- The RTT between two main sites in a stretched vSAN cluster
- The RTT between each main site and the witness host in a stretched cluster
The maximum Round Trip Time (RTT) is as follows:
- The RTT between member hosts in a standard vSAN cluster: 1 ms
- The RTT between two main sites in a stretched vSAN cluster: 5ms
- The RTT between each main site and the witness host in a stretched cluster: 200 ms
What license tier is required for advanced vSAN features such as erasure coding, encryption, and deduplication, and compression?
An advanced or enterprise level license.
What is the default policy assigned to a vSAN?
The default vSAN policy includes the following:
- A PFTT of 1
- A single disk stripe per object
- Thin-provisioned virtual disks
What term best describes the following?
“Software components that integrate with vSphere to provide information about the physical storage capabilities.”
Storage Providers (or VASA Providers).
Which type of storage provider manages storage arrays and handle abstraction of physical storage?
Persistent storage providers.
What type of storage provider is used for host-based caching, compression, and encryption?
Data storage providers.
What service enables ESXi hosts to communicate with storage arrays?
VAAI, also known as hardware acceleration or hardware offload APIs.
What is the purpose of derivatives in regards to VAAI operations?
To offload storage operations to the storage array itself, this increases performance and reduces overhead.
Without VAAI hardware offloading, which service is responsible for storage array operations such as copying data from the source datastore to the destination datatore?
VMkernel Data Mover.
Which VAAI block primitive replaces the use of iSCSI reservations on VMFS datastores?
Atomic Test and Set (ATS)
What is the purpose of the ATS Only Flag in regards to VAAI Block Primitives?
The ATS Only Flag primitive forces ATS to be used rather than relying on SCSI reservations for all metadata updates and operations.
Which VAAI block storage primitive allows the VMkernel to offload cloning or Storage vMotion migrations to the storage array?
The XCOPY (Extended Copy) primitive.
Which VAAI block storage primitive is used with Eager zeroed thick-provisioned disks, and allows the storage device to write zeros for the disk?
The Write Same (Zero) block storage primitive.
What VAAI NAS primitive is functionally identical to the XCOPY block storage primitive, but is used for NAS devices as opposed to block storage devices?
The Full File Clone primitive.
Which VAAI NAS primitive best describes the following?
“Allows snapshot creation to be offloaded to the storage device for use in linked clones? Typically in VMware Horizon or vCloud Director.”
The Fast File Clone/Native Snapshot Support primitive.
What is the purpose the the Extended Statistics VAAI NAS primitive?
Allows the ESXi host to have insight into space utilization on a NAS device.
Which VAAI NAS primitive best describes the following?
“A primitive that allows thick provisioning of virtual disks on NAS datastores.”
The Reserve Space primitive.
Describe the purpose of the Thin Provisioning Stun in regards to VAAI Thin Provisioning Primitives.
Priori to version vSphere 5.0, all virtual machines would be paused when their respective thin-provisioned datastore reached 100% utilization. With the Thin Provisioning Stun, only virtual machines requiring more store are paused. Other VMs are not effected.
Which Thin-Provisioning VAAI primitive is used when a VM is migrated to a different datastore or is deleted?
Thin Provisioning Space Threshold Warning.
With the VAAI Thin Provisioning Space Threshold Warning primitive, how is space reclaimed when a VM is migrated or deleted?
The ESXi host uses SCSI UNMAP commands to tell the storage array that the space can be reclaimed.
What term best describes the following?
“Pools of raw storage or aggregations of storage capabilities that a storage device can provide to vVols.”
Storage Containers.
What term best describes the following?
“Encapsulations of VM files and disks that are stored natively on the storage containers.”
vVol Objects.
Describe the purpose of Protocol Endpoints in regards to vVols.
To address I/O from an ESXi host to a storage array and acts as proxies for vVols and virtual disk files.
With vVols, where are data service such as snapshots, replication, and encryption offloaded to?
To the storage array.
What are the 5 types of virtual volumes (vVols)?
Config-vVol: Metadata
Data-vVol: VMDKs
Mem-vVol: Snapshots
Swap-vVol: Swap files
Other-vVol: Vendor solution specific
Describe the limitation of vVols.
Limitations of vVols include the following:
- Cannot be used with a standalone ESXi host
- vVols do not support RDMs
- a vVol storage container cannot span different physical arrays
What versions of failover are supported by ESXi multipathing?
Fibre Channel failover
Host-based failover with iSCSI
Array-based failover with iSCSI
Path failover and virtual machines
Describe the function of Pluggable Storage Architecture (PSA).
To provide a way for storage vendors to provide their own multipathing policies which uses can install on ESXi hosts.
What submodules are used by the VMware NMP?
Storage Array Type Plug-ins (SATPs) and Path Selection Plug-ins (PSPs).
What submodules of VMware NMP are responsible for array-specific operations?
Storage Array Type Plug-ins (SATP)s
Which NMP submodules is used for handling path selection for I/O requests for storage devices?
VMware Path Selection Plug-ins (PSPs).
What is the purpose of Storage Polices?
To define which datastores to use when placing a virtual machines disks.
What are the 3 types of Storage Policies that can be implemented in vSphere?
- VM storage polices for host-based data services
- VM storage policies for vVols
- VM storage polices for tag-based placement
Which type of virtual disk type zeros out the entire virtual disk at the time of creation; effectively provisioning the entire virtual disk?
Eager Zeroed Thick.
What type of virtual disk type allocates the entire space upfront, but only zeros out the blocks as the space is demanded?
Lazy Zeroed Thick.
Which type of virtual disk is neither allocated or zeroed out at the time of creation and is allocated and zeroed out on demand?
Thin Provisioned.
Which vSAN policy describes the following?
“This policy determines the number of capacity devices where each VM object replica is striped.”
Number of Disk Stripes per Object.
What is the default and maximum settings for the Number of Disk Stripes per Object policy?
Default setting is 1, maximum is 12.
Describe the function of the Flash Read Cache Reservation vSAN policy.
This policy defines the amount of flash capacity that is reserved for reach caching of VM objects, expressed as a percentage of the size of the VMDK.
What is the default and maximum settings for the Flash Read Cache Reservation policy?
Default setting is 0%, maximum is 100%.
What is the default setting for the Force Provisioning vSAN policy?
Default setting is no.
What vSAN policy describes the following?
“This policy defines the percentage of VMDK objects that must be thick provisioned on deployment.”
Object Space Reservation.
What are the options for the Object Space Reservation vSAN policy?
- Thin provisioning (Default)
- 25% reservation
- 50% reservation
- 75% reservation
- Thick provisioning
What vSAN policy describes the following? What is the default value?
“A checksum is used to validate the integrity of data to ensure copies of data are the same as the original.”
Disable Object Checksum, default is no.
Describe Space Utilization Load Balancing in regards to Storage DRS (SDRS).
To generate recommendations or automatically perform Storage vMotion migrations to balance space usage across the datastore cluster.
Describe I/O Load Balancing in regards to Storage DRS (SDRS).
To generate recommendations or automatically perform Storage vMotion migrations to balance I/O across the datastore cluster when I/O exceeds a latency threshold.
Describe the 3 available SDRS automation levels.
- No Automation (Manual): Placement and migration recommendations are only displayed, but not run automatically.
- Partially Automated: Only placements are run automatically, migrations recommendations are only displayed
- Fully Automated: Both placements and migrations are run automatically
Describe the purpose of the Space Utilization Difference threshold in regards to SDRS.
This threshold verifies that there is a minimum difference in space utilization between source and destination before making a recommendation.
Which SDRS threshold describes the following?
“After this interval, SDRS runs to balance I/O load.”
I/O Load Balancing Invocation Interval.
Lowering which value makes I/O load balancing less aggressive?
I/O Imbalance Threshold.
When does SDRS make mandatory recommendations?
SDRS will make mandatory recommendations in the following scenarios:
- A datastore becomes full
- Anti-affinity or affinity rules are being violated
- When a datastore enters maintenance mode
Describe the function of Affinity and Anti-Affinity rules in regards to Storage DRS.
To ensure that a set of virtual machines are stored on the same (Affinity) or separate datastores (Anti-Affinity).
Describes the difference between Network I/O Control (NIOC) and Storage I/O Control (SIOC).
NIOC allocates network bandwidth to business critical applications, whereas SIOC allows you to control the amount of storage I/O that is allocated to VMs using shares and limits.
