Dell DES-6332 Q&A: Why VxRail administrator does not find any compatible datastores when trying to create storage policy?

Question

A VxRail deployment has eight nodes. The VxRail administrator does not find any compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding.

What is the likely reason?

A. vSAN datastore used capacity is above 80%
B. Erasure coding is only supported on all-flash systems
C. vSAN capacity reserve has been enabled
D. Fault domains have not been configured yet

Answer

C. vSAN capacity reserve has been enabled

Explanation 1

Answer: D. Fault domains have not been configured yet

Explanation: In a VxRail deployment with eight nodes, when a VxRail administrator cannot find any compatible datastores to create a storage policy with FTT=2 and FTM=Erasure Coding, the most likely reason is that fault domains have not yet been configured.

Erasure Coding, particularly RAID-5 (FTT=1) or RAID-6 (FTT=2), requires a specific minimum number of hosts in separate fault domains to work correctly. If fault domains have not been defined, then the vSAN will not recognize the configuration as valid, and compatible datastores will not be available when attempting to create the storage policy.

To resolve this issue, the administrator should configure fault domains according to the requirements of their specific storage policy and FTT (Failure to Tolerate) configuration. This will ensure that the Erasure Coding feature can be utilized, and the vSAN datastore will become compatible.

Based on the Google results and our existing conversation, it appears that the likely reason for not finding compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding in an eight-node VxRail deployment is that fault domains have not been configured yet.

Explanation 2

The correct answer is D. Fault domains have not been configured yet.

Fault domains are logical groupings of hosts that share a common point of failure, such as a rack or a power supply. Fault domains are required for creating a storage policy with FTT=2 and FTM=Erasure Coding on a VxRail cluster. Erasure coding is a method of data protection that splits data into fragments and adds redundant data pieces to enable data recovery in case of failures. Erasure coding requires at least four fault domains for RAID 5 (FTT=1) and six fault domains for RAID 6 (FTT=2).

The other options are incorrect because:

A. vSAN datastore used capacity is above 80%: This would not prevent the creation of a storage policy, but it would affect the performance and availability of the cluster².
B. Erasure coding is only supported on all-flash systems: This is true, but it does not explain why the VxRail administrator does not find any compatible datastores³.
C. vSAN capacity reserve has been enabled: This is a feature that reserves a percentage of the vSAN datastore capacity for future use, but it does not affect the creation of a storage policy.

Explanation 3

The likely reason why the VxRail administrator does not find any compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding is B. Erasure coding is only supported on all-flash systems.

Erasure coding is a data protection technology that can be used to improve the availability of data in vSAN. It works by distributing data across multiple disks and then encoding it using a mathematical algorithm. If a disk fails, the data can be reconstructed from the remaining disks.

Erasure coding is only supported on all-flash systems. This is because it requires a high-performance storage system that can handle the additional processing overhead of encoding and decoding data.

If the VxRail deployment has hybrid disks, the administrator will need to create a storage policy with FTT=1 and FTM=Mirroring. Mirroring is a data protection technology that creates two copies of each data block on separate disks. If a disk fails, the data can be reconstructed from the remaining copy.

Here are some additional details about the other possible answers:

A. vSAN datastore used capacity is above 80% – This is not the likely reason, as the administrator would have received an error message if the datastore was full.
C. vSAN capacity reserve has been enabled – This is not the likely reason, as the administrator would have received an error message if the capacity reserve was in use.
D. Fault domains have not been configured yet – This is not the likely reason, as fault domains do not affect the compatibility of storage policies.

Explanation 4

The correct answer is D. Fault domains have not been configured yet.

RAID 5 or RAID 6 erasure coding enables vSAN to tolerate the failure of up to two capacity devices in the datastore. You can configure RAID 5 on all-flash clusters with four or more fault domains. You can configure RAID 5 or RAID 6 on all-flash clusters with six or more fault domains.

Therefore, if the VxRail administrator does not find any compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding, it means that the cluster does not have enough fault domains to support this configuration. The administrator needs to configure at least six fault domains for the cluster before creating the storage policy.

The other options are incorrect because:

A. vSAN datastore used capacity is above 80%. This would not prevent the administrator from creating a storage policy, but it might trigger a rebalance operation to free up some space on the capacity devices.
B. Erasure coding is only supported on all-flash systems. This is true, but it does not explain why the administrator does not find any compatible datastores. The question implies that the cluster is an all-flash system, otherwise the administrator would not be able to select Erasure Coding as a failure tolerance method.
C. vSAN capacity reserve has been enabled. This is a feature that allows the administrator to reserve some capacity for future use or for maintenance operations. It does not affect the creation of storage policies, but it reduces the usable capacity of the vSAN datastore.

Explanation 5

A. vSAN datastore used capacity is above 80% is not likely because the administrator would not be able to create any new storage policies if this were the case.
C. vSAN capacity reserve has been enabled is not likely because the administrator would still be able to create storage policies, but the capacity reserve would be applied to the new storage policies.
D. Fault domains have not been configured yet is not likely because fault domains are not required for vSAN to function.

Erasure coding is a data protection technique that can be used to improve the resilience of vSAN datastores. Erasure coding divides data into multiple blocks, which are then stored across multiple disks. If a disk fails, the data can be reconstructed from the remaining disks.

Erasure coding is only supported on all-flash systems because it requires a large amount of CPU and memory resources. All-flash systems have enough CPU and memory resources to support erasure coding without impacting the performance of the vSAN datastore.

If you are using a hybrid system, you can still use erasure coding by creating a dedicated all-flash fault domain. This will allow you to use erasure coding for your most important workloads, while still maintaining the flexibility of a hybrid system for less demanding workloads.

Here are some additional tips for using erasure coding:

Use a dedicated all-flash fault domain for your most important workloads. This will ensure that your most important data is protected even if a disk fails.
Monitor your vSAN datastores for performance degradation. Erasure coding can impact the performance of your vSAN datastores. If you notice any performance degradation, you may need to increase the number of disks in your fault domain.
Keep your vSAN software up to date. Dell regularly releases updates that improve the performance and reliability of erasure coding.

Explanation 6

Erasure coding is only supported on all-flash systems and not on hybrid systems.

Explanation 7

Erasure coding is a data protection technique that spreads data across multiple disks in a vSAN datastore. This technique can provide higher availability and performance than traditional RAID techniques, but it requires more storage capacity. All-flash systems have enough storage capacity to support erasure coding, while hybrid systems may not.

Here are some additional details about the other possible answers:

A. vSAN datastore used capacity is above 80% – This is not the likely reason, because the VxRail administrator would have received an error message if the datastore used capacity was above 80%.
C. vSAN capacity reserve has been enabled – This is not the likely reason, because the VSAN capacity reserve would not prevent the administrator from creating a storage policy with FTT=2 and FTM=Erasure Coding.
D. Fault domains have not been configured yet – This is not the likely reason, because fault domains are not required for erasure coding.

Explanation 8

The likely reason for not finding any compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding is B. Erasure coding is only supported on all-flash systems. Erasure coding is a method of data protection that uses less storage capacity than mirroring (RAID 1), but requires all-flash clusters to perform well.

Some other information about erasure coding are:

Erasure coding enables vSAN to tolerate the failure of up to two capacity devices in the datastore.
Erasure coding requires four or more fault domains for RAID 5 and six or more fault domains for RAID 6.
Erasure coding is a policy attribute that can be applied to virtual machine components through vSAN policies.

Explanation 9

The likely reason the VxRail administrator does not find any compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding is D. Fault domains have not been configured yet.

Explanation:

In a VxRail deployment, a fault domain is a logical grouping of hosts. They are used to determine how data is distributed across the cluster to ensure its availability in the event of a failure. When you configure fault domains, Virtual SAN ensures that protection objects, such as replicas and witnesses, are placed in different fault domains.

When you set a storage policy with FTT=2 (Failure To Tolerate = 2), it means that the system can handle up to two concurrent failures without data loss. This requires the data to be replicated across multiple hosts.

Erasure Coding (FTM=Erasure Coding) is a method that allows for data recovery in case of a failure. It breaks data into fragments that are expanded and encoded with redundant data pieces and stored across a set of different locations or storage media.

The FTT=2 and FTM=Erasure Coding configuration requires a minimum of 6 fault domains (hosts) for RAID-6 (Erasure Coding). In this case, the VxRail deployment has eight nodes, which is sufficient. However, if fault domains have not been configured yet, the system cannot distribute the data and its replicas correctly across the different hosts. This would prevent the creation of a compatible datastore with the desired storage policy.

Therefore, the correct answer is D. Fault domains have not been configured yet.

Explanation 10

The likely reason in this scenario is B. Erasure coding is only supported on all-flash systems.

Erasure coding is a data protection mechanism in vSAN that provides resilience to failures by distributing data across multiple hosts in the cluster. It allows for the reconstruction of data in the event of a failure, using mathematical calculations. However, erasure coding is only supported on all-flash systems in VxRail.

If the VxRail deployment has eight nodes and the administrator is unable to find any compatible datastores when trying to create a storage policy with FTT=2 and FTM=Erasure Coding, it suggests that the VxRail system does not have an all-flash configuration.

All-flash systems in VxRail typically use solid-state drives (SSDs) for storage, which provide higher performance and better endurance compared to traditional spinning disk drives (HDDs). Erasure coding, on the other hand, introduces additional computational overhead, which may impact the overall performance on hybrid (HDD/SSD) configurations.

To resolve this issue and enable the creation of a storage policy with erasure coding, the administrator would need to ensure that the VxRail system is configured with all-flash nodes. This may involve adding or replacing the existing nodes with all-flash nodes that are compatible with the VxRail system.

It’s important to consult the specific VxRail documentation and compatibility matrix to determine the supported configurations and requirements for erasure coding and other advanced features.

Explanation 11

Answer: The correct answer is D. Fault domains have not been configured yet.

Explanation: Fault domains are logical groupings of hosts that share a common physical failure point, such as a power supply or a network switch. Fault domains are used to ensure that data is distributed across different failure points to increase availability and resilience. When using erasure coding as a failure tolerance method (FTM), fault domains must be configured to match the number of failures to tolerate (FTT). For example, if FTT=2, then at least three fault domains must be configured, each with at least one host. In this scenario, the VxRail deployment has eight nodes, but no fault domains have been configured yet. Therefore, when the VxRail administrator tries to create a storage policy with FTT=2 and FTM=Erasure Coding, they do not find any compatible datastores because there are no fault domains that can satisfy the policy requirements. To solve this issue, the VxRail administrator must configure fault domains for the cluster before creating the storage policy.

Reference

Dell Specialist Systems Administrator VxRail Appliance Exam DES-6332 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Dell Specialist Systems Administrator VxRail Appliance Exam DES-6332 exam and earn Dell Specialist Systems Administrator VxRail Appliance Exam DES-6332 certification.