Fred Liu via illumos-discuss wrote:
Solaris has live patching, but not live activation of kernel patches -
a reboot is required.
Most of the Illumos distros do the same.
Are there any document about these stuff?
Yes. These are called Boot Environments. They are not only used for live
patching, but also snapshots for rollback for sysadmin convenience e.g.
for configuration changes.
In Solaris 10 and earlier, it's called Live Upgrade - same idea, but
completely different implementation.
Sun did live activation of kernel patches over 10 years ago (Project
DUKS - https://blogs.oracle.com/jimmo/entry/the_fate_of_hot_patching)
but never productized it. The hard part is not the kernel live patching,
but the management infrastructure that records precisely what you are
running, and that was beyond the capabilities of the packaging system
in use back then. Oracle has said they are revisiting this in Solaris,
now that Solaris has a packaging system which can handle it (IPS) and
Oracle have the Ksplice technology in their Linux.
In open source Linux world there are also the similar technologies like
kpatch/kGraft.
In fact, dynamic software updating (DSU) is just in research stage and not
widely used in industry. "Retrofitting" current OS may not deliver thorough live patching
which needs innovations in bundle of hardware(like mainframe) and kernel and programming languages.
But any effort to minimize service outage is valuable.
I think it is also the guideline for "zpool|zfs upgrade" command
operation even I played them on-the-fly without any issues. But ZFS is
already a proven *enterprise* storage solution, we should definitely
expect the minimum service outage just like NetApp/EMC.
When you want that level of availability, clustering is normally used,
and ZFS works fine in clusters (at least in Solaris/Illumos - I don't
know about ZoL).
ZFS is not native cluster file system. Cluster needs extra software stacks.
HA is always a really touchy and tricky topic. It is application-specific and
involves different levels of HA.
What solution works well with ZFS in Soaris/Illumos? Sorry if it is off-topic
and we may start a new thread.
Sun Cluster/Oracle Solaris Cluster is the vendor implementation from
Sun/Oracle, and it did work with OpenSolaris, but I don't know if anyone
has tried it with OpenIndiana. I have heard of it being tested
successfully in one of the other Illumos distros.
High-Availability.com offer their own HA cluster implementation for
Solaris and for several of the Illumos distros, which supports making
zfs datasets highly available, and things like NFS/SMB/iSCSI/FC shares
based on zfs datasets.
I would guess that Veritas Cluster can also do at least some of this,
but I'm less familiar with it.
--
Andrew Gabriel
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