RE: Root volume LS mirror best practices?

Justin> Another pretty major difference between LS and DP methods;
Justin> DP method requires manual intervention when a failover/restore is needed.

This is fine in my case, because I'm really trying to protect against
a shipping failure, though it's tempting to do more to protect against
root volume failures as well.  Though I've honestly never had one, nor
had a netapp fail so badly in 22+ years of using them that I lost data
from hardware failures.

Closest I came was on a F740 (I think) using the DEC StorageWorks
canisters and shelves.  I had a two disk failure in an aggregate.  One
disk you could hear scrapping the heads on the platter, the other was
a controller board failure.  Since I had nothing to lose, I took the
good controller board off the head crash drive and put it onto the
other disk.  System came up and found the data and started
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.

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).

The default for 9.3 seems to be 1 hour, but I bumped it to every 5
minutes, because I have Netbackup backups which use snapshots and 'vol
clone ...' to mount Oracle volumes for backups.  I had to hack my
backuppolicy.sh script to put in a 'sleep 305' to make it work
properly.

Trying to make it work generically with 'snapmirror update-ls-set
<vserver>:<source>' wasn't working for some reason, so the quick hack
of a sleep got me working.


But I am thinking of dropping the LS mirrors and just going with DP
mirrors of all my rootvols instead, just because of this issue.


But let's do a survey, how many people on here are using LS mirrors of
your rootvols on your clusters?  I certainly wasn't across multiple
clusters.

Jhn

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