>>>>> "Chris" == Chris Hague <Chris_Hague@ajg.com> writes:
Chris> Yeah it’s interesting that they aren’t created automatically.
Chris> It could have something to do with issues it causes. Especially
Chris> if you are using SRM \ SRA within an NFS VMWare environment.
We're using ESX NFS datastores, so now I'm wondering if I've
potentially screwed myself over at some point.
It might just be smarter to make snapmirrors of my various VServer
rootvols instead. It's not like I've ever had any performance issues
with my rootvols, and now I have to wait 5 minutes for changes (vol
clone... vol mount ...) to take effect, or push the updates manually.
I honestly think this is a poor design which could be improved.
John
Chris> From: Toasters <toasters-bounces@teaparty.net> On Behalf Of André M. Clark
Chris> Sent: 30 April 2021 14:20
Chris> To: Scott M Gelb <scottgelb@yahoo.com>; Parisi, Justin <justin.parisi@netapp.com>; Scott M Gelb
Chris> via Toasters <toasters@teaparty.net>; John Stoffel <john@stoffel.org>
Chris> Subject: Re:
Chris> [EXTERNAL]
Chris> One thing that I have always thought about with SVM root vol protection is, if it is an
Chris> operational recommendation, why aren’t they automatically created in a System Manager workflow
Chris> when a NAS SVM is created? Things to make you say, Hmmmmmmmn
Chris> From: Scott M Gelb via Toasters <toasters@teaparty.net>
Chris> Reply: Scott M Gelb <scottgelb@yahoo.com>
Chris> Date: April 28, 2021 at 16:46:47
Chris> To: Parisi, Justin <justin.parisi@netapp.com>, John Stoffel <john@stoffel.org>
Chris> Cc: toasters@teaparty.net <toasters@teaparty.net>
Chris> Subject:
Chris> I have used both DP and LS over the years and am back to using LS more often for reasons
Chris> Justin wrote, and also for an NAE/NVE workaround where DP make-vsroot had some hoops to jump
Chris> through to re-create the mirrors after a failover test. LS mirror promote and recreate after
Chris> had no issues with NAE/NVE in my testing. In all the years doing this, I've never had to
Chris> recover svm root, but to follow best practices for NAS, still implement them. I don't create
Chris> mirrors on all nodes and use 1-2 copies depending on cluster size.
Chris> An interesting test in mirror activation, is that the mirror picks up the existing SVM
Chris> junctions regardless of the state of SVM root mirror. For example:
Chris> 1) An SVM has 4 junction paths
Chris> 2) SVM root mirror LS or DP to protect SVM root
Chris> 3) unmount 3 of the junction paths leaving 1 junction path
Chris> 4) failover to the root mirror (promote LS or break/make-vsroot DP)
Chris> 5) SVM root running on the failed over volume has the 1 junction path, not the 4 that
Chris> existed at the time of the mirror... there was no real failure, and the procedure with the
Chris> SVM running keeps the current state. If a real disaster, I would expect recovery to what
Chris> was in the mirror, but have never had to recover svm root.
Chris> An RFE on my wish list is to have the SVM root virtualized in the RDB, then we don't need to
Chris> manage, replicate or ever move SVM root. I know this isn't an easy task and would use mroot/
Chris> vol0, and cause more cluster traffic, but still would welcome seeing a change to do this if
Chris> feasible. Not a show stopper or requirement, nor high priority.
Chris> On Wednesday, April 28, 2021, 11:24:12 AM PDT, John Stoffel <john@stoffel.org> wrote:
Justin> Another pretty major difference between LS and DP methods;
Justin> DP method requires manual intervention when a failover/restore is needed.
Chris> This is fine in my case, because I'm really trying to protect against
Chris> a shipping failure, though it's tempting to do more to protect against
Chris> root volume failures as well. Though I've honestly never had one, nor
Chris> had a netapp fail so badly in 22+ years of using them that I lost data
Chris> from hardware failures.
Chris> Closest I came was on a F740 (I think) using the DEC StorageWorks
Chris> canisters and shelves. I had a two disk failure in an aggregate. One
Chris> disk you could hear scrapping the heads on the platter, the other was
Chris> a controller board failure. Since I had nothing to lose, I took the
Chris> good controller board off the head crash drive and put it onto the
Chris> other disk. System came up and found the data and started
Chris> rebuilding. Whew! Raid-DP is a good thing today for sure.
Justin> LS Mirrors are running in parallel and incoming reads/access
Justin> requests (other than NFSv4) hit the LS mirrors rather than the
Justin> source volume, so if one fails, you don’t have to do anything
Justin> right away; you’d just need to resolve the issue at some
Justin> point, but no interruption to service.
Chris> That's a decent reason to use them.
Justin> LS mirrors can also have a schedule to run to avoid needing to
Justin> update them regularly. And, if you need to write to the SVM
Justin> root for some reason, you’d need to access the .admin path in
Justin> the vsroot; LS mirrors are readonly (like DP mirrors).
Chris> The default for 9.3 seems to be 1 hour, but I bumped it to every 5
Chris> minutes, because I have Netbackup backups which use snapshots and 'vol
Chris> clone ...' to mount Oracle volumes for backups. I had to hack my
Chris> backuppolicy.sh script to put in a 'sleep 305' to make it work
Chris> properly.
Chris> Trying to make it work generically with 'snapmirror update-ls-set
Chris> <vserver>:<source>' wasn't working for some reason, so the quick hack
Chris> of a sleep got me working.
Chris> But I am thinking of dropping the LS mirrors and just going with DP
Chris> mirrors of all my rootvols instead, just because of this issue.
Chris> But let's do a survey, how many people on here are using LS mirrors of
Chris> your rootvols on your clusters? I certainly wasn't across multiple
Chris> clusters.
Chris> Jhn
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