Thunderbolt performance

[warrenl]

I have a 5K iMac. I believe the thunderbolt speed is related or shared over one bus.

I have an external Lacie Thunderbolt drive, as well as a OWC ThunderBay 4, four-bay drive enclosure with dual Thunderbolt 2 ports.

If I connect the Lacie into the Thunderbay 2nd port, I lose 75 MB/s write speed, but keep the same read speed.

My second Thunderbolt port I use for an secondary monitor using a mini display port to DVI adaptor.

My question is, how much data transfer does a monitor use compared to an external Thunderbolt drive? If i connect the monitor into the 2nd thunderbolt port, how much of a performance hit will I get?

 

[loekf]

I have a 5K iMac. I believe the thunderbolt speed is related or shared over one bus.

I have an external Lacie Thunderbolt drive, as well as a OWC ThunderBay 4, four-bay drive enclosure with dual Thunderbolt 2 ports.

If I connect the Lacie into the Thunderbay 2nd port, I lose 75 MB/s write speed, but keep the same read speed.

My second Thunderbolt port I use for an secondary monitor using a mini display port to DVI adaptor.

My question is, how much data transfer does a monitor use compared to an external Thunderbolt drive? If i connect the monitor into the 2nd thunderbolt port, how much of a performance hit will I get?

4K display: 3840 x 2160 x 60 fps x 3 bytes-p-pixel = 1.4 GB/s (11 Gbps).. not taking protocol overhead (10/8 coding ??)
into account, so let's say 60% if a TB2 connection. There should be plenty of room for an external drive.

 

[warrenl]

The monitor is Dell u2410, not a 4k monitor. I switched the Lacie from the back of the Thunderbay to the iMac 2nd TB port, and purchased a longer monitor cable (12') as the Thunderbay is as far away from my desk as I can get it on a 3m TB cable due to fan noise.

On running tests after the monitor/lacie switch, I see better performance on the Laice TB external, and no loss of performance on the Thunderbay with the monitor attached. In fact I am getting improved read/writes of about 20MB/s without the Lacie attached, which is basically the same as the Thunderbay without any attached TB devices.

 

[matreya]

I have a 5k iMac also, with a total of 8 Thunderbolt enabled drives on the two ports, and I've never noticed any speed drops. I have no Lacie drives though. 2 x Thunderbay IV, a G-Tech RAID array, a Lacie esata hub, a Mercury Elite Pro Dual & a Buffalo DriveStation on one branch, and 2 x Thunderbay 4 minis & an OWC Mercury On-The-Go-Pro thunderbolt connected SSD.

I would suspect the Lacie TB External...

 

[warrenl]

Thanks for the feedback. Have you ever compared the speed of a single device on TB, compared to multiple at the same time?

I get the same speed on my SSD if it is in the Thunderbay or the Lacie, but as mentioned not if the Lacie is connected to the Thunderbay.

 

[matreya]

I've performed multiple file copies from a RAID0'd 4 x 500GB SSDs to my hard drives in both Thunderbays and not noticed any speed decreases... I monitor my disk traffic with a free open source tool called XRG

http://www.gauchosoft.com/Products/XRG/

I thought the Lacie was an external TB HDD - you swapped out the HDD to put in an SSD?

 

[warrenl]

Yes, I put a 500GB Crucial SSD in the Lacie TB enclosure