The document discusses integrating Samba with Gluster and FUSE. It notes that Samba expects POSIX behaviors that Gluster can provide, like cache coherency and POSIX locking support. FUSE presents a problem as it locks away Gluster internals. The document proposes that the Samba VFS layer could allow Gluster features to be selectively enabled or disabled per access method. Building a Samba VFS module for Gluster was discussed but example code was omitted.

1. Gluster Developers Summit ● March, 2013
Copyright © 2013 Christopher R. Hertel
Samba VFS to libgfapiSamba VFS to libgfapi
Driving the BackroadsDriving the Backroads
Christopher R. Hertel
Samba Team Member

2. 22Gluster Dev Summit – March 2013Gluster Dev Summit – March 2013
IntroductionsIntroductions

3. IntroductionsIntroductions
A ruminant mammal (Geekus geekus) with long legs, humped shoulders, and broadly palmated antlers.
Me
Author
Storage Architect
Network Engineer
SMB Know-It-All
Samba Team Member
(since '98)
Incurable Idealist
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4. IntroductionsIntroductions
44Gluster Dev Summit – March 2013Gluster Dev Summit – March 2013
The opinions expressed are my own
and not necessarily those of my
employer, my spouse, my childrenz,
the dog, or “the Voices”.

5. IntroductionsIntroductions
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You

6. IntroductionsIntroductions
66Gluster Dev Summit – March 2013Gluster Dev Summit – March 2013
Members of the Samba Team gather at the 10th
annual
Samba eXPerience conference in Göttingen, Germany.
Them

7. IntroductionsIntroductions
A Note About Me
For good or ill, I have
become...
TheThe source for
SMBv1
documentation,
Purveyor of
protocol
pedanticism, and
Chronicler of
the apopsicle.
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8. IntroductionsIntroductions
[MS­CIFS]
Covers SMB/CIFS as
implemented in
Windows NT and 98.
[MS­SMB] (revised)
Rewritten to reference
[MS­CIFS].
Details changes from
NT4 to W2K through
W2K12 & Win 8.
Lead author of two SMBv1 protocol
specifications, published by Microsoft:
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9. IntroductionsIntroductions
Let me get this straight...
Microsoft contracted with
a Samba Team member
to produce
publicly available
SMB protocol
specifications!?
Wait... What?
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10. IntroductionsIntroductions
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Where are we going?
Overview of SMB and Samba
Samba and Gluster and FUSE, oh my
The Samba VFS layer
Building Samba VFS modules
Missing Pieces
Questions
(and answers, if I have any)

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Where we are not going:
We won't go into libgfapi internals
I rely on others for libgfapi know-how

13. What's in a Name?What's in a Name?
A Rose by Any Other NameA Rose by Any Other Name
WouldWould
Wither and DieWither and Die
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­­ Alan Swann (Peter O'Toole),
My Favorite Year

14. What's in a Name?What's in a Name?
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SMBSMB: Server Message Block
Originally, a simple network file protocol
created by IBM. It grew, over time, to include
75 primary commands and an unbounded
number of secondary commands.
CIFSCIFS: Common Internet File System
A 1990's marketing upgrade. CIFS is just
another name for SMB1. Microsoft officially
dropped the CIFS name in 2012.
SMB1SMB1: A new name for SMB, as implemented in
Windows NT and still used in Windows today.
SMB2SMB2: A new protocol intended to eventually replace
SMB1. SMB2.0 was included in Windows
Vista. SMB2.1 in W2K8r2 and Windows7.
SMB3SMB3: Just another dialect of SMB2 (specifically
SMB2.2). SMB3 adds support for cluster
and multipath features.

15. What's in a Name?What's in a Name?
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SMBSMB = Server Message Block
DOS, OS/2, and Windows
CIFSCIFS == SMB1
SMB1SMB1 = SMB on Windows,
starting with NT
SMB2SMB2 = New SMB,
introduced in Vista
SMB2.0 = Vista
SMB2.1 = Win7 / W2K8r2
SMB3SMB3 = SMB2.2 = Win8 / W2012
The naming is confuzzeling. Keep these charts handy.

16. What's in a Name?What's in a Name?
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Samba and CTDB
SambaSamba = SaMBa
An Open Source SMB server,
Full support of SMB1 (and older)
Partial support of SMB2/3
Samba v4 is the current production
branch.
CTDBCTDB = Cluster Trivial Database
A distributed key⇨value database,
Maintains Samba state across
a cluster
Also provides IP failover

17. What's in a Name?What's in a Name?
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Samba
is...
An SMB protocol engine, and...
A semantic translation machine:
Different locking
Different access controls
Different timestamps
Different just about everything
Samba has to translate from
Windows to POSIX and back again.

18. What's in a Name?What's in a Name?
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CTDB is...
A Distributed DatabaseA Distributed Database
Tables are replicated on every node
Persistent tables are updated atomically
Volatile tables use a token-passing
scheme; the “owner” has current data:
data will be lost when a node crashes
...and that's okay!
In theory,
CTDB's functionality could be replaced...

19. What's in a Name?What's in a Name?
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State of the Art:
Samba and SMB2/3
Samba has full support for SMB1
Samba can negotiate SMB2
SMB2 features are limited
SMB3 cluster features are missing

20. What's in a Name?What's in a Name?
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State of the Art:
SMB3 cluster features
Scale-out
Transparent Failover
Client/server negotiated
CTDB does not yet support failover
CTDB (or its replacement) must support
SMB3 Persistent Handles

21. What's in a Name?What's in a Name?
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SummarySummary
What we need from Samba:
SMB3 cluster features
What we need from CTDB:
Persistent handle support
What we need from Gluster:
Internal support for
Windows semantics
ACLs, Leases, etc.
Persistent Handles?

23. Samba and Gluster
and FUSE

24. Samba/Gluster/FUSESamba/Gluster/FUSE
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“Samba is a semantic translation machine”
—We said that already
Samba translates from Windows to
POSIX and back again
Samba expects POSIX behaviors:
Cache Coherency
POSIX byte-range locking support
Samba also wants Linux FS features:
Extended Attributes
“POSIX” ACLs
RichACLs (would be nice)

25. Samba/Gluster/FUSESamba/Gluster/FUSE
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Gluster
...is adaptable, and cool.
Can add support for
SMB-specific features:
Windows ACL support
OpLocks and Leases
Case-insensitive names
Can selectively enforce
semantics:
Share modes
Preallocation
Other stuff
There are possibilities to explore here.

26. Samba/Gluster/FUSESamba/Gluster/FUSE
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FUSE
...presents a problem.
A generic mount point
No way to enable/disable per-access
method features
Fuse provides a single
standard interface, but
effectively locks away
Gluster internals.
What's a coder to do?

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The Samba VFS layerThe Samba VFS layer

29. The Samba VFS LayerThe Samba VFS Layer
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Samba is Built in Layers
(conceptually)
SMB messages received
and parsed
(Non-FS commands are
handled elsewhere)
Call the VFS layer
The final VFS module talks to
the File System
Upper layers may bypass
lower layers

30. The Samba VFS LayerThe Samba VFS Layer
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If there's no real File System,
bypass the lower VFS layers
All VFS calls must be implemented
(possibly returning ENOTSUP)
to avoid errors.

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Building a Samba VFSBuilding a Samba VFS

33. The Samba VFS LayerThe Samba VFS Layer
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There is a guide:
Writing a Samba VFS by Richard Sharpe
Unfortunately...
The Samba VFS Interface changes as new
features are added
VFS modules must be kept in sync with
Samba releases
VFS developers need to coordinate with
Samba developers

34. ??
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Example code and such was s'posed to go here.
I'll work out a good place to put the code and we'll start a project...

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36. The EndThe End
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