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10GbE Mac mini/iMac Pro Slow Transfer Speeds

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Dipak Ramkumar
10GbE Mac mini/iMac Pro Slow Transfer Speeds
on Jan 19, 2019 at 2:30:51 pm

Hi,

I am trying to troubleshoot my network setup and hoping to get some advice on the problem. Here is my current setup:

Mac Mini 2018 with 10G ethernet port, connected to an external thunderbolt 3 SSD. Read/write speeds according to Blackmagic are about 1500 MB write and >2k MB read. The external drive has been shared through system preferences (i.e. file sharing through SMB).

The Mac Mini is acting as the "server" in my set up. My "client" is an iMac Pro. Both machines are connected to a Netgear GM110X switch with Cat7 cable. iperf3 indicates 9.91 Gb link between the two computers.

The problem is, when I used Blackmagic Speedtest to test the read/write speeds on either the Mac Mini external SSD or the internal SSD, the max speeds I get are around 700 write/750 read. This appears to be about half the actual 10Gb bandwidth. I have taken both computers off the switch and direct connected them as well, to ensure this was not a switch issue, and read/write speeds are exactly the same.

I have jumbo frames enabled on both computers by manually changing the MTU to 9000. The switch also supports jumbo frames automatically.

Any thoughts on what I am doing wrong here?

Thanks!


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Bob Zelin
Re: 10GbE Mac mini/iMac Pro Slow Transfer Speeds
on Jan 19, 2019 at 6:57:08 pm

Hi
I cannot find the Netgear GM110X switch, so I cannot identify which switch you are using.
this is the budget series of small Netgear 10G switches -
https://www.netgear.com/business/products/switches/unmanaged/XS505M.aspx

your Mac Mini is the server which is not a great server, but it will work. However, are you using a single SSD, or an SSD RAID. You cant have shared storage with a single SSD or SATA drive - you must have multiple drives in a RAID configuration for this to work.

As for your speeds, 10G max throughput is 1250MB/sec theoretical, and even with a properly setup system, with modern equipment, you are lucky to get 900 - 1000 MB/sec. So 700 MB/sec is great, and it can do 8K. Don't rely on iPerf, as it only measures the network speeds. Use the utilities from AJA or Blackmagic for your speed tests.

The iMac Pro 10G port to any shared storage system that has a 10G port and eight drives in a RAID config will do
900 - 1000 MB/sec read and write speed. The Mac Mini has a single thunderbolt buss, that you will be sharing with your 10G port and your RAID array.

You have jumbo frames enabled which is correct. Make sure that you have disabled SMB signing.

Again - you can be doing "everything" correctly, but you are not going to get a shared storage system to work with only one single SSD drive.

Bob Zelin

Bob Zelin
Rescue 1, Inc.
bobzelin@icloud.com


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Roy Pearson
Re: 10GbE Mac mini/iMac Pro Slow Transfer Speeds
on Jan 21, 2019 at 8:02:49 pm

Bob,

I'm pretty sure the new Mac Mini 2018 has two TB3 busses (four ports total). Maybe you're thinking of the old 2012 model and that's why you say it's not a great server?

Roy


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Bob Zelin
Re: 10GbE Mac mini/iMac Pro Slow Transfer Speeds
on Jan 21, 2019 at 11:31:47 pm

you are correct Roy. The new Mac mini has four thunderbolt ports, 2 busses, and an optional Aquantia 10GbE port.
With that said, this gentleman is not going to get the performance he expects from one single SSD for a workgroup.

Bob Zelin

Bob Zelin
Rescue 1, Inc.
bobzelin@icloud.com


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Dipak Ramkumar
Re: 10GbE Mac mini/iMac Pro Slow Transfer Speeds
on Jan 21, 2019 at 11:40:03 pm

Thanks everyone for their prompt responses!

We are in the process of building a custom NVME SSD array. I currently have one 2TB NVME SSD connected to the Mac mini 2018 (which has its own, dedicated 10GbE port) via thunderbolt 3. This is just shared using the SMB file sharing protocol in OS X. SMB signing has been disabled.

When attempting to test the access speed to this external SSD using an iMac Pro (also with its own dedicated 10GbE) port, the max write speeds I am seeing are around ~700 and reads around ~750 MB/sec. The NVME SSD through TB3 (accessed directly on the Mac) has read/write speeds over 2,000 MB/sec. Assuming my 10Gb link is working appropriately, I would expect around a 1000 MB/sec transfer rate to this drive. I am assuming the speeds that I am getting are getting limited by the SMB protocol, which seems to be associated with high transfer overhead. Unfortunately, I cannot use AFP since all Macs in the deployment are already running High Sierra or Mojave. I guess NFS would be another option, but its not clear to me how to specifically set this up for an external SSD in Mac OS. It appears that this was previously doable using the GUI in OS X server tools, but this is no longer possible.

I appreciate everyone's expertise and advice.


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