samba - Feb 2022 - Windows User Profile corruption on a member server

12.02.2022 13:16, Michael Tokarev via samba wrote:
..

I did some experiments here with user profiles. And it turned out
the prob is quite severe. Lots of files, when copied from the samba
server to windows10 machine, gets truncated. Small files can be truncated
by a few bytes, larger files loses some blocks (the resulting size is usually
dividable by 20480). Out of 104 total files in a freshly created win10
user profile, 40 gets corrupt. This is a huge number, this is 40% corruption
ratio, it is not some random very rare event.

And this is independent on the user presence in /etc/passwd - the same
(similar, since it is different each time) corruption happens if the user
in question exists as local linux user or not.

There are no errors reported on either side.

With this corruption samba is definitely not usable as a file server, at all.

Any idea where to go from here?

(samba is 4.13.13+dfsg-1~deb11u2, current on debian bullseye system).

Thanks,

/mjt

12.02.2022 22:27, Michael Tokarev via samba wrote:
...

So I tried to debug this further. And it seems this has nothing to do
with samba per se, it is some problem with windows. Maybe samba is
somehow related to this too, but not within its file operations which
are done exactly as windows client asked it.

What I see here is that windows, while copying a user profile from
the (samba) server (when this profile didn't exist), first creates
small portion of each file, something in chunks of 20480 bytes.
Yes it reads these 20480 bytes from samba and samba happily does
what it was asked.  So win populates whole thing with these small
portions of each file, and immediately starts the user GUI. But
neither the wallpaper nor the StartMenu links are complete at this
time, and lots of other files too.  But it continues to syncronize
this profile "in the background", writing all data (including these
first 20480 bytes) this time (and ofc. asking samba to read all the
data this time)..  I don't know where it stops (and it stops before
completing), but the end result is still the same - lots of profile
files become incomplete/corrupt.

Regular file copy works fine from both samba and windows PoV. Only
the profile sync is this awful, so far.

So far I only observed this strange behavor when using a linux server
joined to the AD domain (hence the subject). But I remember seeing
something similar before with our previous setup too, - very very
rarely. I dunno what the difference is, - the server is actually the
same (just a new container on the same hardware, with similar settings).

On the client we use Windows 10 LTSC 1809 with current updates.
I'll probably install some over version of Win10 to see if it
behaves differently.

The whole thing is.. just terrible :)

Thanks,

/mjt

On Sat, Feb 12, 2022 at 10:27:11PM +0300, Michael Tokarev via samba
wrote:
>12.02.2022 13:16, Michael Tokarev via samba wrote:
>..
>
>I did some experiments here with user profiles. And it turned out
>the prob is quite severe. Lots of files, when copied from the samba
>server to windows10 machine, gets truncated. Small files can be truncated
>by a few bytes, larger files loses some blocks (the resulting size is
usually
>dividable by 20480). Out of 104 total files in a freshly created win10
>user profile, 40 gets corrupt. This is a huge number, this is 40% corruption
>ratio, it is not some random very rare event.
>
>And this is independent on the user presence in /etc/passwd - the same
>(similar, since it is different each time) corruption happens if the user
>in question exists as local linux user or not.
>
>There are no errors reported on either side.
>
>With this corruption samba is definitely not usable as a file server, at
all.
>
>Any idea where to go from here?
>
>(samba is 4.13.13+dfsg-1~deb11u2, current on debian bullseye system).
Is it possible that it is this bug ?

https://bugzilla.samba.org/show_bug.cgi?id=14928

Fixed in latest 4.15.x, 4.14.x.