about "ea support" parameter

[Leo Fan]

Thanks Andrew, your information is helpful!

-Leo

From: Andrew Walker <awalker at ixsystems.com>
Date: Friday, November 27, 2020 at 9:12 AM
To: Ralph Boehme <slow at samba.org>
Cc: Leo Fan <xfan at vmware.com>, "samba-technical at lists.samba.org" <samba-technical at lists.samba.org>, Albert Guo <aguo at vmware.com>
Subject: Re: about "ea support" parameter



On Thu, Nov 26, 2020 at 5:30 AM Ralph Boehme via samba-technical <samba-technical at lists.samba.org<mailto:samba-technical at lists.samba.org>> wrote:
Am 11/26/20 um 10:57 AM schrieb Leo Fan via samba-technical:
> Hi samba experts,
>
> I need your help to understand the smb.conf parameter ‘ea support’.
> We are developing a customized samba service to serve Windows 10
> clients and MAC OS clients. And, we would like to set ‘EA support =
> no’ to gain more performance of ‘dir’ command especially on the large
> directory, but as smb.conf doc says, EA support disablement will
> impact Windows file service compatibility.
>
> The default has changed to yes in Samba release 4.9.0 and above to
> allow better Windows fileserver compatibility in a default install.

To give you some background: that change untangled the previous mixture
of configuring both SMB level behaviour *and* backend storage behaviour.
Nowadays this parameter only configures the SMB level behaviour, ie if
we support EAs in the protocol. There are various ways a client get
list, get and set EAs over SMB, by setting "ea support = no" all of
those will fail with an error, probably NT_STATUS_NOT_SUPPORTED.

However, if when setting "ea support = no" Samba will still use xattrs
in the backend as storage for various bits and pieces like DOS
attributes, creation date, ACLs and so on.

> I am not quite clear about compatibility problem with EA support
> disablement, and have some questions:
>
>
> 1.  In which scenarios will there be windows file service
> compatibility?

As explained above, you disable something which a Windows server
supports. Hell may brake loose or you may never notice a difference in
client behaviour, you never know.

> 2.  How do we create and use EA?

There are various SMB info level to get and set them, cf MS-FSA/MS-FSCC.

> 3.  Does any well-known Windows/MAC application use EA?

I'm not aware of any.
Windows Subsystem For Linux uses them, but unsure of implications over SMB protocol (haven't looked into it). IIRC, Illumos disables EA support by default in their SMB server implementation for performance reasons for directory listing.

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