Performance Monitoring..

I have a Thunderbay Mini 4 enclosure filled with 2TB 2.5" hard disk drives arranged either as RAID 1 + 0 or RAID 5. These don't seem to last very well. Initially an easy 100MB/sec plus per drive on large files in the TB4 Mini. But after a month or five the transfer rate drops a great deal - sometimes.

Testing the drives using AJA System Test Lite, I can see that writes have a problem. The transfer rate varies across the GB of data, hitting 100MB/sec sometimes and dropping to 4 or fewer MB/sec for some substantial amount of data. Looks like a noisy square wave.

I attach a .pdf document showing results for the worst drive (with the disks in a USB-2 connected Voyager S3, so max speed is 38MB/sec). 

But to do this I need to delete the volume, reformat the drives with Disk Utility, and then measure. 

So, to the point: could you consider adding a "test this disk drive's performance" capability that would do something like what the Aja test does, on a drive still part of a volume, using some blocks which were not part of a file? Even better if the results were shown in a manner similar to Aja's

Thanks!