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th0masp

macrumors 6502a
Original poster
Mar 16, 2015
815
479
I have multiple Macs hooked up in a wired Gigabit network here - there's no central always-on server, instead they all have SMB shares configured and I'm transferring data between them by mounting the desired share on whatever is my current machine I'm using.

What I noticed is that between two of my machines there's a big discrepancy in transfer speeds: basically fetching data from the remote machine works as expected but sending data (even to the very same share during the same session) is orders of magnitude slower because the transfer (via Finder) stalls frequently. It looks like some buffer is being filled and then things grind to a halt for a few seconds.

Both machines are configured identically in network preferences and set to 1000baseT, I have disabled SMB package signing and tried the hack sudo sysctl -w net.inet.tcp.delayed_ack=0 on them to no avail. Also have set jumbo-frames on both machines.

Large files are affected the same way as folders full of small files are.

Any idea how to fix this?
 

th0masp

macrumors 6502a
Original poster
Mar 16, 2015
815
479
No, still the same behaviour here. Pretty sure I caught this 'feature' when upgrading the OS at one point.
 

HDFan

Contributor
Jun 30, 2007
6,458
2,752
I am having a similar problem with SMB shares from a QNAP and a Synology. My iMac 10GbE Mohave port is connected to a 10 GbE switch which is then connected to the QNAP 10 GbE port and the 1 GbE Synology port.

I have no problems with the QNAP, where I can transfer data up to about 160 MB/s. Transfers to the Synology are slow, on the order of 15 MB/s.

If I move the iMac connection to a 1 GbE Asus router which is connected to the 10 GbE switch my connection on the Synology increases to ~110 MB/s. However the QNAP connection now drops down to the 10 MB/sec range.

Summary:

iMac > 10 GbE switch > (QNAP, Synology)
QNAP ~150 MB/s
Synology ~15 MB/s

iMac > Asus 1 GbE router > 10 GB Switch > (QNAP, Synology)
QNAP ~ 15 MB/s
Synology ~100 MB/s
 
Last edited:

th0masp

macrumors 6502a
Original poster
Mar 16, 2015
815
479
One thing I'll have to look into is if the same transfer speed issues affect protocols other than SMB. Not going to go back to AFP however - I have a Windows machine here, too.
 
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