Resolving Low Write Buffer Free Percentage in All-Flash vSAN Cluster
Question
An All-Flash vSAN cluster has 4 nodes with this disk group composition on each host: -> 1 Ã- 800 GB SAS SSD -> 6 Ã- 3.84 TB SATA SSD An administrator observes that in an All-Flash cluster, the Write Buffer Free Percentage is consistently low.
As a result, there is increased latency experienced by the workloads.
Which remediation steps will resolve this issue?
Answers
Explanations
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A. B. C. D.C.
In an All-Flash vSAN cluster, the Write Buffer Free Percentage being consistently low can result in increased latency experienced by workloads. This issue can be resolved by taking the following remediation steps:
Option A: Add a second disk group with a new cache device and distribute the capacity disks equally. This option involves adding a new disk group with a cache device and distributing the capacity disks equally across both disk groups. By doing so, the workload I/O will be spread across both disk groups, which will increase the cache hit rate and reduce the latency. However, adding a new disk group will also result in additional hardware costs.
Option B: Add a second cache device to the same disk group to increase the caching size. This option involves adding a second cache device to the existing disk group, which will increase the size of the cache and reduce the latency. However, this option requires that the hardware used in the existing disk group supports multiple cache devices, and adding a second cache device may also result in additional hardware costs.
Option C: Modify advanced vSAN configuration parameters to utilize the complete 800 GB for caching. This option involves modifying the advanced vSAN configuration parameters to allow the cache device to utilize the entire 800 GB for caching. By doing so, the cache hit rate will increase, which will reduce the latency. However, this option may result in reduced capacity for storing data.
Option D: Replace the existing cache device with a larger cache device. This option involves replacing the existing cache device with a larger cache device. By doing so, the cache hit rate will increase, which will reduce the latency. However, this option may also result in additional hardware costs.
In summary, options A and B involve adding hardware to the existing configuration, whereas options C and D involve modifying the existing hardware configuration. The best option depends on the specific requirements and constraints of the environment, such as the available hardware and budget, and the expected workload.
