Is there any lower limit on Disk Image IO bandwidth

[harishpathangay]

Hi,
I am using VBOX 6.0.8. r130520 with Ubuntu Mate Linux Guest, Host Win 10.
Trying to use IO bandwidth on Virtual Hard Disk Image of 2GB capacity, formatted with xfs file system.
created bandwidth group "IOB" with io speed 1KB/sec. Associated the 2GB drive with IOB bandwidth group.
But I am getting 1.5MB/sec when I copy a 1.2GB file as data transfer rate, iostat output displays kb_written/sec as 1.5MB/sec
Is there are any lower limit on IO bandwidth?

please find attached the vbox xml config file.

thanks,
harish pathangay

[mpack]

The manual says that this feature only applies to asynchronous I/O, so what happens if you enable the "Use host I/O cache" option on the controller?

[harishpathangay]

hi,
host I/o cache is not enabled. did not test it.
the command I am using for test is
dd if=/dev/zero of=/media/iob/dblog/laptop.bin bs=512 oflag=direct
the above command fills up entire disk of 2GB.at the rate 1.4mbps.
I understand I am performing direct io on the command, but not sure whether it is asynchronous.

in other words, I just want to go to the lowest io rate as possible in io bandwidth feature of virtual box.
not sure what is that minimum rate of io.

thanks,
harish p