copies of these files are getting slower and slower

[vl at samba.org]

On Wed, Apr 26, 2017 at 07:37:06AM -0700, Richard Sharpe via samba-technical wrote:
> On Wed, Apr 26, 2017 at 1:18 AM, Liuxuan via samba-technical
> <samba-technical at lists.samba.org> wrote:
> > Hi,everyone:
> >
> > Recently,I meet a performance problem ,when I use Samba 4.2.11 to copy files from windows to linux. copies of these
> > files are getting slower and slower quickly. But when I set the “case sensitive = yes” in smb.conf, it works very well.
> > Can anyone help me? How should I deal with this problem when I use case “sensitive = yes”?
> >
> > The protocol is SMB2_10 and file size is 105KB.
> 
> This is a well known issue. Since Samba is trying to provide the same
> semantics as Windows, eg Case Preserving, Case Insensitive, when you
> try to create a file, it:
> 
> 1. stat's the name as presented to check for existence, but if that fails,
> 2. It has to search the directory for case-equivalent names.
> 
> Only if 2 fails can it go ahead and create a new problem.
> 
> This is an O(N^2) problem.
> 
> By telling Samba that the file system is case sensitive you skip step
> 2. However, there be dragons unless you actually have a file system,
> like XFS or ZFS that can do case-insensitive lookups ...

In addition: In case the original poster is working for an OEM with
control over the file system, the OEM should take a look at the
getrealfilename VFS operation that can hook into case-insensitive
indexing operations inside a case-sensitive file system. This was
created for GPFS, which can do an efficient case-insensitive search
with a special ioctl.

Volker