Does Avigilon ACC Server Spread The Load Between Storage Volumes?

This seems promising. I can't imagine any other argument for such an algorithm than to balance load.

I wouldn’t count on it doing any fine grained load balancing, without seeing some documentation describing it.

What Parvinder is saying, IMHO, is that Avigilon will generally use use space on the volumes equally.  But besides that there is no guidance.

And there could be many reasons that they wouldn’t just implement a round-robin device write.

First off, when you add the volume it’s empty, therefore by the first only rule, Avigilon might favor the new drive in an effort to get the volumes to be equally filled.

Then when devices are equal but near capacity (which in surveillence is almost all the time), the primary factor might be what device has the longest contiguous free block, or which one has the best fit.  Or threads handling particular streams may be assigned certain handles, meaning that a high bitrate camera could cause asymmetrical writes favoring certain drives.

That’s why it can be better to let the OS/Raid handle the physical implementation of the logical file thru abstraction.

It’s easy enough to get a rough idea by test though, have you looked at your I/O stats after adding a new volume?

iSCSI, Direct attached, FC?   How much incoming throughput do you have from the cameras?