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Slow and Unresponisve Transfers Using SMB2

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TabascoJoe

Occasional Visitor
Hello
RT-AC68U with FW 382.2_beta3. USB3 EXT3 drive connected.
When SMB2 is enabled the transfer speeds going from the router to a Windows 10 system is slow. It starts out strong with a 20 to 30 MBs transfer, but quickly drops below 1 MBs. It will get to the point the transfer fails. This is on a wifi and wired connections.

Now when SMB2 is disabled the transfer speed is a solid 35MBs to 40MBs (btw WOW, best speeds out of any router I've seen).

I like to use SMB2 as SMB1 is not enabled on Windows 10 by default. I don't like the hassle of enabling it on all systems. What could be causing the erratic speeds on SMB2? Is it Windows or the AC68U? Thanks.
 
As I understand it SMB2 is much more compute intensive... but that wouldn't explain why it starts out at 20 and drops to 1
 
Why does the interface show Enable SMB2 protocol (default: No).
Is SMB2 that buggy that is not on by default?
 
Why does the interface show Enable SMB2 protocol (default: No).
Is SMB2 that buggy that is not on by default?

Probably because it is so much more compute intensive and is a relatively new addition to the firmware.
 
Why does the interface show Enable SMB2 protocol (default: No).
Is SMB2 that buggy that is not on by default?

Because it slows down performance by about 10% on older routers. It's only enabled by default on the RT-AC86U, as on that model it doesn't slow down performance in any measurable way.
 
With the FW 384.4 and newer the Changelog reads. "Ideally, people should change it to SMBv2 only". I went back to SMB2 and still the speeds are slow to unresponsive with the 2nd core max out at 100%. There is no way ideally I'm sticking to SMBv2 only. There has got to be an issue with the code as SMBv1 rock a solid 30 to 40MBS. I see above you state a 10% hit, I'm experiencing a 110% hit.

issue.PNG
 
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Just noticed that the max CPU and 0 bytes transfer is from the USB drive attached to the RT-AC86U transferring down to a Windows box (wired or wireless). If transferring up to the AC68U it's slow (around 5MBs) but never max CPU or 0 byte transfer.
 
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Hi, did this problem ever got resolved ? I am facing the same problem and am looking for a bypass that still allows for smb2 to be used..
 
Because it slows down performance by about 10% on older routers. It's only enabled by default on the RT-AC86U, as on that model it doesn't slow down performance in any measurable way.

Sorry to say this, but way more than 10%. In my experience speed is reduced about 80%. Probably due to some AES crypt or something similar not supported (or bad optimized) in ARM7 / 32bits ark.
 
Sorry to say this, but way more than 10%. In my experience speed is reduced about 80%. Probably due to some AES crypt or something similar not supported (or bad optimized) in ARM7 / 32bits ark.

What does AES crypt have to do with Samba?

10% was the numbers I had throughout my tests while implementing this.
 
What does AES crypt have to do with Samba?

10% was the numbers I had throughout my tests while implementing this.

It was just a guess since SMB v2 is safer but way slower (at least in the AC68/AC66_B1) I tend to think is due to some kind of crypt/algorithm which is bad supported by certain SoCs/compilers/kits.

Like those SSSE3 or AvX extensions which you can't find in chips which are more than 5-6 years old.When apps/compilers don't find certain extensions they choose another route to solve the maths, way more basic and compatible, but way slower too.

It's a guess from the behaviour I've seen. Granted SMBv2 is at least about 4-5 times slower in my router than SMBv1 (one large file through wifi). I personally don't have problems keeping SMB v1 in my home. I'm not running any critical service and compatibility is something I value.
 
It was just a guess since SMB v2 is safer but way slower (at least in the AC68/AC66_B1) I tend to think is due to some kind of crypt/algorithm which is bad supported by certain SoCs/compilers/kits.

Samba 3.6.xx doesn't use any encryption.

If your performance drop is higher than 10% then something else is affecting your performance, it's not caused by the SMBv2 protocol alone.
 
Samba 3.6.xx doesn't use any encryption.

If your performance drop is higher than 10% then something else is affecting your performance, it's not caused by the SMBv2 protocol alone.

I don't know the reason. Maybe it's just a bug, a buffer, no idea. The smbd process uses one core at 100% with the SMBDv2 in the AC66_B1.

I've just replicated the test again with the same results.

The first test I did with 384.4 and Windows 10 1709. Today I've done with 384.5 beta 2 and Windows 10 1803.
 
Hi, it is not a 'performance drop' per se, but a sporadic slowdown to as low as 0Kb/sec while transferring large files with SMB2.., as it has already been reported by a few users in the last couple of months (like for instance here https://www.snbforums.com/threads/smb2.42048/#post-356940).

There were some experiments a few months ago regarding the Samba config file, some optimizations done by these users showed good improvements in some scenarios (especially over wifi I believe). I suspect that playing with these settings might help.
 
In this thread we tested various config options and made some significant improvements with SMB, on the AC86U we were able to improve read and write speeds around x2 - x3. Older models the results weren't as high but still much better then default configuration
 
In this thread we tested various config options and made some significant improvements with SMB, on the AC86U we were able to improve read and write speeds around x2 - x3. Older models the results weren't as high but still much better then default configuration
I had the same problem, and it was perfectly resolved by setting "socket options = IPTOS_LOWDELAY TCP_NODELAY SO_KEEPALIVE".
Thank you very much.
 
I had the same problem, and it was perfectly resolved by setting "socket options = IPTOS_LOWDELAY TCP_NODELAY SO_KEEPALIVE".
Thank you very much.

Hi, thank you for the suggestion. Just tried it (I had missing the SO_KEEPALIVE thing) but unfortunately I am still experiencing the slowdowns when copying from the router's samba share through wifi. (does not happen when copying from another windows 10 machine share through wifi)
 
I did some tests on SMB 1 vs 2 on my Mac & it shows that SMB 1 has a much more stable (same speed) connection whereas SMB 2 tends to have a lot of up & down spikes with what should be a higher throughput. In the end, SMB 1 seems more decent for streaming purposes for me & the difference in overall long term speed is almost negligible. This is with the AC3200.
 

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