SUMMARY: DiskSuite Questions

From: Rodney Wines (
Date: Wed Jul 28 1999 - 07:17:09 CDT

Thanks to David Evans, Arthur Dunham, and "OGIRAUD" (full name unknown).

>I've just had to add a couple of disks to a Solaris 2.6 system using
>DiskSuite 4.1 (I think). My changes seem to be working, but I'd
>like to ask a couple of questions while it'd still be easy to reconfigure.
>First, when I start metatool, the MetaDB shows a status of "Attention".
>However, "Show problems" doesn't show anything. Browsing the problem list
>shows, "All replicas are on fewer than three controllers". Is this what
>it's complaining about?

The consensus was, yes. I added a replica to a disk on the third controller,
and the "Attention" message went away.

>Second, the original configuration contained 6 disks. I've added two more;
>one is not being used yet. There are 8 mirrors (the disk I added isn't
>mirrored). The person who originally installed the system created three
>MetaDB replicas per disk. Isn't that a bit of overkill? I only created one
>replica on the new disk I added, which gives us 19 replicas. The
>documentation says that for 5 or more disks, there should be one replica
>per disk.
>The documentation ALSO says there should be one replica per mirror, which
>says I should have 8. What's the correct number? Does it hurt anything to
>have too many?

Yes, it seems that three per drive is overkill, although nobody commented on
whether or not this would actually cause me any problems. I removed the
extras, and now only have one per disk. I removed the extra replicas by
using the GUI to delete the three replicas on a disk and then adding one
back. Since the replicas were in their own partition, this was easy. This
just means that now there is some wasted space in the replica partition.

>Is there anything else I should be worrying about?

It was suggested that I use the command line tools instead of the GUI, but
I'm new to DiskSuite, and I don't expect to have to work with it again any
time soon, so the GUI was much easier to use.

The most important thing to remember about MetaDB replicas is that you have
to plan for failure. If you have disks mirrored across two controllers, but
the controller containing the majority of your replicas fails, the system
won't run even though it theoretically could. The replicas should be spread
among disks and controllers in such a way that if the failure of a component
can be tolerated, there will still be a majority of replicas available if the
component fails.

Again, thanks.


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