I am looking for a disk activity monitor that can tell me how many bytes/sec (or MB/sec) each of the disks attached to my machine are transferring. Something like the network monitor where you can see your send/receive rates, but for disks. System monitor doesn't do it, and it doesn't look like Conky does it. Any other ideas?
I started looking for this because it seems like either Lucid is having some issues with multiple copies running simultaneously to and from the same disks, or I am having difficulty realizing just how much contention there really is. If I start a single copy operation transferring say 100GB of video files from my internal sata disk to a USB attached disk, the copy will run somewhere around 18MB/sec or a little more. If I start a second copy from the same internal disk to the same USB disk, the transfer rates start falling until they get down to around 6MB/sec combined. These numbers are from the "File Operations" dialog. The internal sata disk is formatted ext4, and the USB is ext3.
I get more throughput than that when using Filezilla to transfer files from my media server to this same computer over my 100Mb Ethernet. As a matter of fact, while the file copies are running I can start Filezilla and get about 7.5MB/sec downloading three simultaneous files to the sata drive. I expect the individual transfers to slow down, and maybe the overall throughput to reduce due to disk contention, but I didn't expect it would fall all the way down to 1/3 or 1/4 the rate of a single copy operation. So this is why I am looking for a good disk activity monitor. So I can see what is really happening.