File-Level Backup with VCB Fails When Attempted with Six or More Virtual Disks on the Backup Proxy

File-level backup with VCB fails if an attempt is made to mount many (typically six or more) virtual disks concurrently on the backup proxy when connecting directly to a host.

Currently, VCB opens one connection per disk to the SDK instance it is using (ESX Server or VirtualCenter Server). For ESX Server, the default number of concurrent connections is limited to eight. This limit prevents the possibility of jeopardizing the performance or stability of the ESX Server service console by overloading it with too many instances. Also, some of these eight connections can be used for virtual machine remote consoles, reducing the number of connections available to VCB.

Because VCB has to share this connection pool with other applications (VirtualCenter Server, virtual machine remote consoles, or some management agents), no fixed limit can be given. When you encounter this problem, hostd logs the following message:

 [... 'VmdbSvc' 115477424 error] Max connections reached (8), closing connection 

To work around this issue, VMware recommends that VCB connect to a VirtualCenter Server instead of directly to the ESX Server machine. If you do not use a VirtualCenter Server (standalone ESX Server host), you can increase the total number of concurrent connections that hostd allows by editing /etc/vmware/hostd/config.xml.

Add the following lines to the <vmacore> section of this configuration file to increase the total number of concurrent connections allowed:

<vmdb><maxconnectioncount>100</maxconnectioncount></vmdb>