### Human: Can you tell about Alert - A1101 - MetadataUsageCritical. ### Assistant: Investigating MetadataUsageCritical issues on a Nutanix cluster.. This Nutanix article provides the information required for troubleshooting the alert A1101 - MetadataUsageCritical for your Nutanix cluster.

Alert Overview

The MetadataUsageCritical alert is generated when Stargate detects that metadata disk's global metadata usage goes above the 50% of the statfs_disk_size (not the raw disk capacity).

Sample Alert

For status: WARN

ID : 27fc16df-xxxx-xxxx-xxxx-927b8067b8a9

Output messaging

Check ID130025DescriptionMetadata Usage High.Causes of failureThe cluster either has too many snapshots or too much data is being fingerprinted.ResolutionsReduce metadata size by removing unneeded snapshots, creating snapshots less frequently, creating snapshots of fewer VMs, or expanding the cluster size.ImpactCluster performance may be significantly degraded.Alert IDA1101Alert TitleMetadata Usage HighAlert Smart TitleMetadata usage on Controller VM service_vm_external_ip has exceeded critical_pct%.Alert MessageMetadata usage on Controller VM service_vm_external_ip has exceeded critical_pct%.. TroubleshootingFor troubleshooting the A1101 alert, you need to understand:

How much above the 50% threshold did metadata size growWhich disks in a node are metadata disks, and what is their data filesystem (statfs) sizeWhat is the metadata size stored on this node in a Cassandra ring, and whether the ring is balancedSnapshot chain length and RPOs configured for DR snapshots or third-party backupsAdditionally, understanding the workload a cluster was sized for and features enabled on its storage containers
Check stargate.INFO log to find the reported metadata usage percentage above the 50% threshold:
nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"

Check sizes for disk data partitions:

nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"

Example: 

nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"

Note: Up to 4 SSDs can be used by Cassandra to store global metadata, even if the node is all-flash and has more SSDs, as in the example above.
Find which of the disks on the node store Cassandra metadata: 
nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"

Example:

nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"
Check Cassandra metadata load across the cluster: 
nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"

Example:

nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"
Run the NCC ring_balance_check to make sure the Cassandra ring is balanced. One or two nodes might report higher than the average Load or Owns column. Consider rebalancing the ring to distribute the metadata more evenly in such a case. See KB-1342 for more details on the ring_balance_check.Run the NCC snapshot_chain_height_check to identify whether the snapshot chain is too long. See KB-1732 for more details on the snapshot_chain_height_check.Alternatively, check the longest snapshot chain as follows:
nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"
Check in Prism whether Deduplication is enabled on any of the storage containers in the cluster. Deduplication is ill-advised for some workloads. In such a case, deduplication may increase metadata footprint without providing expected capacity savings. For more information on workloads suitable for deduplication, see Deduplication Best Practices chapter in the Prism Web Console Guide.Run the NCC cassandra_ssd_size_check to identify possibly undersized SSD tier in a node. See KB 8842 for more details on cassandra_ssd_size_check.

Resolving the Issue

If the above-mentioned steps do not resolve the issue, consider engaging Nutanix Support.

Collecting Additional Information

Before collecting additional information, upgrade NCC. For information on upgrading NCC, see KB 2871.Collect the NCC output file ncc-output-latest.log. For information on collecting the output file, see KB 2871.Collect Logbay bundle using the following command. For more information on Logbay, see KB 6691. 
	nutanix@CVM:~$ allssh "grep MetadataUsage ~/data/logs/stargate.INFO"
	

Attaching Files to the CaseAttach the files at the bottom of the support case on the support portal. If the size of the NCC log bundle being uploaded exceeds 5 GB, Nutanix recommends using the Nutanix FTP server due to supported size limitations. See KB 1294.. ### Human: Now explain this as a Nutanix support agent summarizing the answer step by step. In case, you don't know the answer say - I don't know.