Grid-enabling Zones

While trying to get the details on the new zones snapshot capability on my Nevada build 41 laptop, I ran the ol' trusty gender-neutral "man" command. I missed it the first time, but not the second. New to the build are "attach" and "detach":

         Detach the specified zone. Detaching a zone is the first
         step  in  moving  a zone from one system to another. The
         full procedure to migrate a zone is  that  the  zone  is
         detached,  the  zonepath  directory  is moved to the new
         host, and then the zone is attached  on  the  new  host.
         Once  the zone is detached, it is left in the configured
         state. If you try to install or clone  to  a  configured
         zone  that  has been detached, you will receive an error
         message and the install or clone subcommand will not  be
         allowed to proceed.

attach [-F]
        The  attach  subcommand  takes  a  zone  that  has  been
         detached  from  one system and attaches the zone on to a
         new system. Therefore, the detach subcommand must be run
         before  the  "attach"  can  take  place.  The zone being
         attached must first be configured using the zonecfg (see
         zonecfg(1M))  command. Once you have the new zone in the
         configured state, use the attach subcommand  to  set  up
         the  zone  root instead of installing. The -F option can
         be used to force the zone  into  the  "installed"  state
         with no validation. This option should be used with care
         since it can leave the zone in an unsupportable state if
         it  was  moved  from  a source system to a target system
         that is unable to properly host the zone.

With attach and detach, a zone can be detached, migrated to a different host, and then attached. Note, this is not an on-the-fly running zone pause and resume capability. The zone must be shut down before being detached. As one engineer put it, its more like a "move" of a zone than a "migration".

One idea is to install the zone with its mount point on an NFS file system or shared SAN (e.g. QFS).  With a shared network fileystem, any system in the grid (running essentially the same OS image) can boot the migrated zone. I recall reading this request on the zones forum roughly 18 months ago.

I have to do a bit more investigation to find out exactly how close we are to actually putting a zone on a grid in such a manner, but at a minimum the foundation is being layed.

I'll have to test this out on my laptop. Thank goodness I have my 2nd internal drive installed on my laptop. That's another 100GB of zones and zfs space to play (ahem - work) with.

Oxymoron: Doing 90% of one's distributed computing on a single laptop :)

This looks an awful lot like VMwares Vmotion / Xen VM migration. They both rely on a SAN in a similar way. If so, Sun should be marketing the f-ck out of this asap. Great work!

Posted by Dick Davies on June 13, 2006 at 01:47 AM PDT #

Does Sun support running zones on NFS storage? The last I heard, this was not supported, and required a good deal of work to get working. It would be AWESOME to be able to store zones on NFS storage. - Ryan

Posted by Matty on June 13, 2006 at 08:39 AM PDT #

Dick/Matty, I don't want to oversell what I've seen so far. As for Vmotion and Xen VM migration, this will not pause a running zone and resume it on another host. The zone actually has to be shut down first.

As for the NFS storage, I am not sure if we are there yet. I know it is a goal.

FWIW, I just detached and attached a zone on my laptop. Pretty boring :) I don't have another system in a similar configuration to move the zone to.

Keep in mind that the system you move the zone to should have the same set of packages, patches, etc. That's why I think a rack (or racks) of similarly configured hardware is a good fit.

I'm going to do more investigation and hopefully will get chance to post a followup.

Posted by John Clingan on June 14, 2006 at 02:01 AM PDT #

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