From Newsgroup: comp.misc
Geoff Clare <
geoff@clare.see-my-signature.invalid> wrote:
Marco Moock wrote:
ZFS should be compatible - at least with Solaris and Linux
For "Solaris" variants derived from Open Solaris (i.e. systems
now built from the Illumos source), that should be true. However,
I think ZFS in actual Solaris (i.e. 11.4 from Oracle) might not
be compatible with BSD and Linux any more, as I seem to recall
reading that their ZFS and Open ZFS have diverged.
ZFS has 'feature flags' to manage this. When you install an old disc in a
new machine, 'zpool status' asks if you want to upgrade your flags to the current version. If you upgrade you get access to more features but lose backward compatibility with the OS the disc was originally used with. If
you don't you retain backwards compatibility.
I believe the Illumos and OpenZFS people have different extensions
controlled by different sets of feature flags. So I think you can keep compatibility if you stick to a baseline set of features. The same applies when upgrading to a newer OpenZFS - if you allow new feature flags then you
can no longer use the disc with the older OpenZFS.
$ sudo zpool status pool
pool: pool
state: ONLINE
status: Some supported and requested features are not enabled on the pool.
The pool can still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
the pool may no longer be accessible by software that does not support
the features. See zpool-features(7) for details.
$ man zpool-features
ZPOOL-FEATURES(7) BSD Miscellaneous Information Manual
NAME
zpool-features rCo description of ZFS pool features
DESCRIPTION
ZFS pool on-disk format versions are specified via rCLfeaturesrCY which
replace the old on-disk format numbers (the last supported on-disk
format number is 28). To enable a feature on a pool use the zpool
upgrade, or set the feature@feature-name property to enabled. Please
also see the Compatibility feature sets section for information on how
sets of features may be enabled together.
The pool format does not affect file system version compatibility or
the ability to send file systems between pools.
Since most features can be enabled independently of each other, the
on-disk format of the pool is specified by the set of all features
marked as active on the pool. If the pool was created by anrCE other
software version this set may include unsupported features.
Identifying features
Every feature has a GUID of the form com.example:feature-name. The
reversed DNS name ensures that the feature's GUID is unique across all
ZFS implementations. When unsupported features are enrCE countered on a
pool they will be identified by their GUIDs. Refer to the
documentation for the ZFS implementation that created the pool for
information about those features.
Each supported feature also has a short name. By convention a
feature's short name is the portion of its GUID which follows the rCy:rCO
(i.e. com.example:feature-name would have the short name
feature-name), however a feature's short name may differ across ZFS
implementations if following the convention would result in name
conflicts.
[snip]
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