hotadd async I/O unsupported, WHY?

[zaqik]

Hello!

I look through logs, and see this text

Code: Select all

transport mode: [hotadd], max sectors to read/write: [8192], async I/O: [unsupported]

Why could possibly async I/O be unsupported for hotadd? I've changed VBR VM (it's a Default Proxy) SCSI Controller type to VMware Paravirtual and it didn't help and sincerely I'm out of options to guess. Can you suggest me a direction to dig?

[Sturniolo]

HI there.. welcome to the forums...

That log entry isn't tied to the proxy VM's SCSI controller type, which is why switching to PVSCSI didn't change anything.

Based on the VMware/Broadcom VDDK documentation, asynchronous I/O support is associated with the NBD/NBDSSL transport modes rather than HotAdd transport. Since your job is running in transport mode: [hotadd], seeing async I/O: [unsupported] appears to be expected behavior and not an indication of a failure.

If backups are completing normally and performance is acceptable, this alone usually is not something to worry about. If you're troubleshooting an actual performance issue, then opening a support case would make sense so the data mover logs can be reviewed in detail.