On Wed, Jul 2, 2014 at 12:42 PM, John Andersen
On 7/2/2014 8:59 AM, Greg Freemyer wrote:
All,
I happened to run a USB3 throughput test recently and it wrote 5 TB in 7 hours. I used a USB3 hub to let me hook up 5 1 TB drives and wrote to them simultaneously.
That's about 200 MB / sec.
It's the first time I've ever apparently saturated USB3. Does anyone know if 200MB / sec is a good max USB3 throughput?
fyi: Per the spec, it should be possible to hit 500MB/sec., but real world seldom hits the spec limits so 200MB/sec may be as good as it gets. If not, I may need to look for a better USB3 hub. (I do a lot of high bandwidth transfers in my job.)
Greg -- Greg Freemyer
Using what method did you write to 5 drives simultaneously?
Something similar to "dd if=/dev/zero of=/dev/sdb" for sdb, sdc, sdd, sde, and sdf individually. I actually used "dc3dd wipe=/dev/sdb" etc. It is more efficient than reading from /dev/zero. It was not a broadcast mechanism.
Best I know, is that you can send data to ONE usb device at a time based on the addressing scheme, and sending to 5 required 5 send operations each with a different address.
I did not mean the same level of simultaneous that you are. I meant the data packets were interleaved. Think: dc3dd wipe=/dev/sdb & dc3dd wipe=/dev/sdc & dc3dd wipe=/dev/sdd & dc3dd wipe=/dev/sde & dc3dd wipe=/dev/sdf I actually used 5 consoles and ran one each of the above in each console.
Multicasting exists for control operations (everybody wake up) but not transfers.
Also, there are many different data transfer modes, and if your software supported synchronous mode you get much better speed than with polled (quick removal) mode.
Does the linux block device stack have a way to support that? I use only a handful of tools typically to bang on these drives, so I could conceivably submit patches to the user space apps to support that if it's a logical thing to do. fyi: I'm hashing (similar to md5sum) 500 GB of data on one drive currently. I'm getting 108 MB across USB3 from a single USB3 drive. I'm very happy with that speed. But when I first copied the data between 2 drives I was only getting about 60 MB /sec throughput (120 MB combined reads and writes). It would be great if I could get a faster transfer than 60 MB/sec. Greg
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