> On Dec 18, 2023, at 3:33 AM, Martin Wege <martin.l.wege@xxxxxxxxx> wrote: > > On Thu, Nov 30, 2023 at 3:03 PM Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote: >> >>> On Nov 29, 2023, at 10:59 PM, Martin Wege <martin.l.wege@xxxxxxxxx> wrote: >>> >>> Hello, >>> >>> does the Linux NFSv4 server has support for alternate data streams? >>> Solaris surely has, but we want to replace it. As our Windows >>> applications (DB) rely on alternate data streams the question is >>> whether the Linux NFSv4 server can fully replace the Solaris NFSv4 >>> server in that respect. >> >> Hi Martin - >> >> Linux NFSD does not support alternate data streams because none of >> the underlying file systems on Linux implement them. Very much like >> the HIDDEN and ARCHIVE attributes. >> >> I believe Solaris and their storage appliance are the only >> implementations of NFS that do support them, since they have >> implemented streams in ZFS. >> >> Instead, Linux NFSD implements extended attributes (that's what >> our native file systems and user space support). I realize that >> the semantics of those are not the same as stream support. > > SMB server on Linux supports Alternate Data Streams - I was not aware of that support. I need more information about how that is done. > why can't the same be done for NFSv4? I mean, yes the standard NFSv4 protocol provides a way to access these, and NFSD can be made to support that. But where would it store that content? NFSD can support what is readily available from the VFS API. If alternate streams were to become a premier part of the Linux file system stack, it would be straightforward for NFSD to support them. IOW first NFSD needs the communities responsible for the VFS and file systems to implement them. Everyone has to agree on how these are stored, we can't just make something up. Otherwise there is no hope for interoperation between local applications and applications that access these via SMB or NFS. -- Chuck Lever
