upgrade of an iSCSI zpool mirror

[Julien Cigar]

On Thu, Jun 14, 2018 at 02:53:25PM +0100, Frank Leonhardt wrote:
> On 2018-06-11 14:04, Julien Cigar wrote:
> > Hello,
> > 
> > We have a "low-cost" active/passive HA ZFS based filer (with
> > NFS4/SMB/... on top) which consist of two tiny HP Proliant DL20
> > with 2 x 2 To disks in each. <snip>
> > 
> > It works well, but those are still running FreeBSD 10.3 and I'd like to
> > upgrade to 11.x. During the upgrade process the pool should be 
> > read-only
> > available. I planned to do something like:
> 
> > Has anyone ever done something similar and/or does it sound good to 
> > you?
> 
> I've tried various combinations, but not that one I'm afraid. I'm not a 
> fan of iSCSI except as a work-around, but FWIW I can't spot anything 
> wrong with your plan, but I'm not sure where NFS fits in.
> 
> You will probably want to upgrade the zpools at some point (optional).
> 

After some exchanges with people smarter than me in this area I got the
confirmation that "There's no issue with the upgrade path." :)

> I've yet to get a fully redundant ZFS implementation up and running, as 
> other solutions have been more useful - such as sending incremental 
> datasets to a backup at a different location. I've also run it on top of 
> HAST, but it scared me.

Yes, in fact all of this started after a question I started on
freebsd-fs@ some years ago:
https://lists.freebsd.org/pipermail/freebsd-fs/2016-June/023456.html

To my suprise I had a lot of answers and it was an interresting
discussion, you may want to check the whole thread if interested.

> 
> One day I plan to look at heartbeat/pacemaker (available in ports/net), 
> which is supposed to be the thing for it.
> 

Yep, I had an interresting exchange on IRC (#freebsd freenode) about
it some days ago. It would be better than using a CARP only based
solution to failover (which is quite easy to split brain).

> In your situation, I think I'd proceed as follows:
> 
> Set up a spare machine (e.g. desktop).
> Do a zfs send <zoot-dataset> to it.
> Turn off samba/nfs
> Do a zfs send <zoot-dataset> of any last minute changes.
> Make the spare machine live, but read-only.
> 

As a security measure I have already a third "replication machine" 
which zrep from the master, I could make the pool read-only from it

> They relax and do whatever I wanted to reconfigure the rack servers.
> 
> Just a thought!

Thanks :)

> 
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-- 
Julien Cigar
Belgian Biodiversity Platform (http://www.biodiversity.be)
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