sun
   microsystems              Systems Architecture Committee

_________________________________________________________________

Subject:       ZFS Boot Support

Submitted by:  Lori Alt

File:          PSARC/2006/370/opinion.ms

Date:          January 16th, 2008

Committee:     James D. Carlson, Kais Belgaied,  Mark  Carl-
               son, Glenn Skinner.

Product Approval Committee:

               Solaris PAC
               solaris-pac-opinion@sun.com

1.  Summary

This project adds ZFS  booting  capability  to  OpenSolaris,
including ZFS-based Live Upgrade.

2.  Decision & Precedence Information

The project is approved as specified in references  [1]  and
[2].

The project may be delivered in a minor release  of  Solaris
via the ON and Install consolidations.

3.  Interfaces

The project exports the following interfaces.

______________________________________________________________________________
|                            Interfaces Exported                             |
|__________________|_______________________|_________________________________|
|Interface         |  Classification       |  Comments                       |
|__________________|_______________________|_________________________________|
|lucreate -p       |  Committed            |  specify root pool              |
|lufslist output   |  Volatile             |  ZFS file system names          |
|ICF entry         |  Consolidation Private|  LU's internal BE data          |
|fstbl             |  Consolidation Private|  LU's internal fs data          |
|lutab             |  Consolidation Private|  LU BE directory                |
|/pooldata/        |  Committed            |  Mount point for common data    |
|canmount=noauto   |  Committed            |  New ZFS property value         |
|pool keyword      |  Committed            |  Jumpstart; specify pool name   |
|bootenv installbe |  Committed            |  Jumpstart; set BE name         |
|__________________|_______________________|_________________________________|

PSARC/2006/370               Copyright 2008 Sun Microsystems

                           - 2 -

______________________________________________________________________________
|                            Interfaces Exported                             |
|__________________|_______________________|_________________________________|
|Interface         |  Classification       |  Comments                       |
|__________________|_______________________|_________________________________|
|filesys keyword   |  Committed            |  Jumpstart; add pool name       |
|rootdev keyword   |  Committed            |  Jumpstart; root pool device    |
|menu.lst          |  Committed            |  Now on SPARC                   |
|zfsboot           |  Project Private      |  ZFS SPARC booter image         |
|/etc/lu/GRUB_slice|  Sun Private          |  Shared LU/bootadm data         |
|ttinstall         |  Volatile             |  Added ZFS configuration screens|
|__________________|_______________________|_________________________________|

4.  Opinion

4.1.  SPARC Versus x86

One member noted that several features (-B  versus  -Z,  and
-L)  in  the booting subsystem differ between SPARC and x86,
and that this could confuse users.  The project team pointed
out  that,  for -B versus -Z, these two options are actually
doing different things, though they happen  to  be  used  to
accomplish  the  same  goal  for ZFS boot.  The -L option is
different because SPARC doesn't have  GRUB.   The  committee
members accepted the project team's explanation.

4.2.  Swap Problems With ZFS

Several members pointed out the deadlock problems with  swap
and  ZFS.   The  project  team  committed to resolving those
problems as a part of (or precondition to)  the  integration
of this project.

4.3.  Xen Support

One member asked how Xen booting,  which  must  extract  the
archive from ZFS early in the boot process, would work.  The
project team did not have an answer for this, but agreed  to
the  stipulation  that it must work, and any changes to that
will require a subsequent review.

4.4.  ZFS Dataset Naming

The project team wished to change its special  "BE"  dataset
container to be less LU-centric and use "ROOT" instead.  The
ARC members agreed, but one ARC member pointed out  that  it
would  be  better  to use an OS-reserved name space for this
ZFS dataset, if possible.  The project team agreed to inves-
tigate  this, but as we know of no such reservation, the ARC
members agreed that using "ROOT" was  sufficiently  unlikely
to  cause  trouble,  given  that  it  appears during initial
install or  during  deliberate  LU  action.   The  reference

PSARC/2006/370               Copyright 2008 Sun Microsystems

                           - 3 -

materials  have  been  updated to use "ROOT," and any change
from that will require a subsequent review.

5.  Minority Opinion(s)

None.

6.  Advisory Information

The project team is advised to investigate a  reserved  name
space  for  ZFS  datasets  that  have special meaning to the
operating system, and use a reserved  name  to  contain  the
boot environments.

The project team is further advised to test Xen booting  and
verify proper operation with ZFS boot.

7.  Appendices

7.1.  Appendix A: Technical Changes Required

None.

7.2.  Appendix B: Technical Changes Advised

None.

7.3.  Appendix C: Reference Material

Unless stated otherwise, path names are relative to the case
directory PSARC/2006/370.

1.   ZFS Boot Specification
     File:  commitment.materials/spec.txt

2.   ZFS Boot For Live Upgrade
     File:  commitment.materials/liveupgrade.txt

PSARC/2006/370               Copyright 2008 Sun Microsystems