SMB share slow and capped at 30MBps

[Johnny Fartpants]

Hi Guys,

Has anyone else noticed that since 11.1 releases SMB has gone really slow? I can achieve near 100MBps on 11.0-U3 and before but anything 11.1 or after is stuck at 30MBps tops.

I have multiple systems pretty much all the same as in my sig and the only difference I can see at the mo is the version of FreeNAS they're running.

When I offer up an AFP share Im back writing at 100MBps or more so it seems like a samba issue.

Cheers

 

[Chris Moore]

It must be a setting, but it hasn't happened to me.

Sent from my SAMSUNG-SGH-I537 using Tapatalk

 

[dlavigne]

I can achieve near 100MBps on 11.0-U3 and before but anything 11.1 or after is stuck at 30MBps tops.

Including 11.1-U4?

 

[Johnny Fartpants]

Including 11.1-U4?

Yep. It was a clean install of 11.1-U4 I noticed it on for two different boxes.

 

[Johnny Fartpants]

Ok I've figured it out. By default when you create a dataset now in 11.1 its says Sync: standard and if I leave it like this and then run a benchmark tool against the share like AJA System on Mac its shows on 30MBps. However if I change the dataset to Sync: Disabled then everything is great again. Not sure in real world testing what issues you would have but nevertheless.

 

[toadman]

Which means whatever the client is it's doing sync writes vs async writes. Do you know the implications of sync=disabled on the dataset and are you ok with those risks? (Which can include losing the entire pool under the right conditions, albeit possibly a rare occurrence, but non-zero.)

 

[Stux]

Or more importantly, it means SAMBA in 11.0-U4 may be respecting sync writes, or enforcing them.

You may want to consider using this diagnostic technique to see a SLOG would resolve the issue:
https://forums.freenas.org/index.php?threads/testing-the-benefits-of-slog-using-a-ram-disk.56561/

 

[Johnny Fartpants]

Thanks for the feedback guys. I found another way which should be potentially less risky which is to leave the dataset as default 'sync standard' and add the auxiliary parameter below to the SMB Global settings.

strict sync = no

 

[KrisBee]

Complaints about poor file transfer speeds over SMB with MAC OS are common on the net.
Suggested fixes include changing the client SMB protocol version and/or turning off client signing.

So what changed between FN 11.0-u3 and FN 11.1? I seem to remember the min/max SMB proctocol settings were removed from the WebUI, so could the answer be that MAC SMB client mount is now using a diiferent SMB version?

The fact that setting the data sync property to disabled restores the higher transfer speeds suggests the MAC OS SMB client is behaving differently to either a Linux or Windows SMB/CIFS client where you'd expect all writes to be async and see no zil activity during a file transfer.

 

[Johnny Fartpants]

I don't think its Mac OS per-say but at the application layer. When I do a normal transfer of data from Mac to FreeNAS all is fine but when I benchmark it with AJA Test I was getting very slow writes. I presume the AJA Test application was utilising the Windows CreateFile API (FILE_FLAG_WRITE_THROUGH) which requests synchronous writes and samba on FreeNAS is now honouring that. Before 11.1 it wouldn't so I assume a change in samba defaults for strict sync from = no to = yes.

I agree in my experience most complaints about poor transfer speeds over SMB from Mac are down to SMB3 signing which can be easily fixed by disabling that on the client end.

 

[KrisBee]

OK, understood and a reminder of the possible pitfalls in benchmarking. You're right testparm -v shows FreeNAS 11.1-x samba now sets "strict sync= yes".

 

[Stux]

Which is a major change as far as user experience goes. It throws the old advise of "you don't need a SLOG if all you want to use is SMB" out of the window.

 

[Johnny Fartpants]

OK, understood and a reminder of the possible pitfalls in benchmarking. You're right testparm -v shows FreeNAS 11.1-x samba now sets "strict sync= yes".

Looking at a 9.10.2-U5 box "strict sync = no" so I would guess that default either changed in 11.0-U4 with (25950 - Update Samba to address current CVEs) or 11.1

 

[Johnny Fartpants]

Which is a major change as far as user experience goes. It throws the old advise of "you don't need a SLOG if all you want to use is SMB" out of the window.

Not completely as if the application doesn't request sync it won't happen.

 

[MrToddsFriends]

Not completely as if the application doesn't request sync it won't happen.

Correct. I didn't see any difference with Windows clients so far. strict sync should not be confused with sync always.
https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html

 

[toadman]

From the smb docs link posted above: "In Samba 4.7.0, the default for this parameter [strict sync] changed from no to yes to better match the expectations of SMB2/3 clients and improve application safety when running against smbd."

Can't remember exactly when FreeNAS pulled in 4.7.0. 11.1-U1 maybe?

 

[dlavigne]

11.1 is when we pulled in 4.7.3 (the first in the 4.7.x series):

1.1. New Features in 11.1

• Samba has been patched to address these security vulnerabilities.

 

[kdragon75]

I would think a PSA would be in order for any such changes in the behavior of FreeNAS, even if done up stream.