How to test USB 3.0 bandwidth usage

Is there a way to test how much bandwidth of your USB 3.0 bus is being utilized at any given time? I'm trying to determine if I have enough theoretical bandwidth to add another major peripheral to it or if I should explore an alternative I/O.
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  1. what are you using? most likely you are not full saturating it
  2. I'm currently at a point where I need to decide whether I should stick with USB 3.0 on my iMac or make the leap to Thunderbolt. Essentially, my end goal is to have two (2) raid boxes each outfitted with 4 or 5 x 3TB HDDs, one of which is used for a time machine backup of multiple machines and the other for every day read/write operations (both direct attached storage and network server-like operations) such as:

    iTunes library which is stored here, edited directly from the iMac and accessed via home sharing for 10GB video files on Apple TV, iPads, etc. Keep in mind that I primarily use Aperture for organizing and deleting photos/videos. I don't do much if any actual editing.

    Aperture photo library which is stored here but is often accessed and edited via remotely but within the WiFi-N network. (The iMac is on 1000mbps LAN.)

    General storage which contains pretty much everything else that isn't OS X or Application based, accessed occassionally.

    The RAID boxes in question are a CineRAID CR-H458 (USB 3.0) and a Drobo 5D (Thunderbolt). Currently, I am using the USB 3.0 CineRAID in a hardware RAID 5 setting (not software based) and it seems to work "OK." Sometimes, I have to wait a few seconds for things to come up in finder and sometimes I need to wait a few seconds for a movie to start playing on ATV3, but in works decently. My question is essentially about bandwidth at this point. I don't want to have the interface be the bottleneck of whatever it is I do. Perhaps it's the case that I'm already maxing out the USB 3 bandwidth of about 5Gbps with the first CineRAID box and just don't know it, or perhaps I'm nowhere near that theoretical almost-5Mbps limit and moving to 10Mbps Thunderbolt would be extreme overkill. That's what I'm hear to gather your opinions on. I realize we don't have any hard numbers to prove anything at this point but in general based off the above information, what would you think? If it's the case that I'm nowhere near maxing out the USB 3.0 bandwidth assuming only the devices above were in use, if I introduced a second CineRAID CR-H458, I'm concerned that I'd be bottlenecking my setup at the USB 3.0 interface. There would be some writing, sometimes heavy writing between both boxes in that case as well.

    Any thoughts from anyone? All are certainly appreciated!
  3. If you're doing things through the network then you'll be bottlenecking that first as it tops out at roughly 100MB/s. Your RAID boxes will easily beat that.
  4. True enough. I just added that network bit to describe the many ways it's being used. Assuming the network bit is not a point of concern (it isn't), I digress back to the original post of how one could objectively measure USB bandwidth usage with direct attached storage (USB 3 vs ThunderBolt).
  5. if you have an SSD (a fast one on SATA3 6GB/s) you could try copying a multiple large files between the SSD and RAID array and monitor the speed in resource monitor. You copy file window will also give you the average transfer speed over the entire file copy period.

    To display Resource Monitor:-
    right click on taskbar -> Start Task Manager -> Performance (tab) -> Resource Monitor (button) -> Disk (tab)
  6. This is an Mac OS X forum, but I do see what you're getting at.
  7. Sorry. I just hit the link on the forum live feed on the front page. I didn't realise it was a mac discussion.
  8. No problem - just need to figure out the best way to measure USB bandwidth in OS X.
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