Symptoms
An Avamar Virtual Machine image backup takes a long time to run and times out before the end of the backup window.Slow-performing image backups cause a bottleneck at the proxy if the pool of image proxies available to service VM clients is insufficient.This leads to queuing whilst the remaining VM clients wait for a proxy to serve them.
Cause
There are many factors that can cause VM image backups to run slowly or take a long time to complete. See the articles below documenting known issues relating to this type of behavior.
Resolution
Step 1: Gather a full set of 'required' information from the customer.It is critical to have a detailed understanding of the environment before starting to troubleshoot the situation. Collect the following:
Avamar - Information to gather when investigating client slow backup performance issues
Also, make a note of:
The version of vCenter in useThe version of the proxy client in use
Step 2: Gather logs for the image backup.
Avamar: How to gather logs for troubleshooting Avamar VMware image backup issues
Step 3: Review known issues. Check the 'troubleshooting' section of the Avamar for VMware User Guide for common issues. Next, check the following;
Check if CBT is enabled for the VM.
See the following VMware articles:
Broadcom VMware article 1020128 Changed Block Tracking (CBT) on virtual machines
b) Check if CBT is enabled for the Avamar VMware Image Dataset
Avamar - VM Image backup performance is slow - logs show Change block tracking (CTK) is supported for this VM but has been declined. This increases proxy CPU and IOP consumption. Avamar - VMware image backups are not using CBT
c) Check if the VM is generating an excessive number of changed blocks.
Avamar VM image backup using CBT is slow due to large number of changed blocks in the virtual disks
d) Check whether the proxy transport mode is using "hotadd" rather than "nbd" or "nbdssl."
Avamar - Fix transport mode to hotadd only in VMware image backupsAvamar VM Image backup occasionally takes longer to complete due to using nbd instead of hotadd
e) Check for any backend storage performance issues.
The customer may open a support case with their vendor if third party support is experiencing an issue.
f) Are CBT image backups running as full backups due to the issue in VMware KB article 2145895?
Step 4: If the issue remains after the above issues have been corrected, escalate to the next level of support.
