Solaris 10 svm - add slice to existing configuration question 1

THis was one answer to the question that I got from Sun.

1) When mirroring, it isn't necessary to do a newfs because when you run the metattach to sync the drives, it will take care of it. If you're not seeing any issues or anything in needs maintenance in metastat, then you should be fine. What you did was pretty much the normal process to setup a simple mirror.

2) Here was the second answer I got on Sun's forum, which says the same thing.

Your getting a little confused about the difference between a partition/slice and a filesystem.
Partitioning is the act of breaking the disk up into "slices". You have been referring to c0t0d0s6 which is a slice. Partitioning is done with the format program.

The filesystem is the data that goes onto the slice. This is what newfs does. It creates a filesystem on a slice. So all its doing is writing a particular pattern of data onto a chunk of disk.

So mirroring filesystems doesnt require a newfs. Since the correct pattern of data already exists. You just need to copy it onto the new slice.
But the mirroring doesnt do partitioning ie create the slice. You have to do that with format. But it does copy the filesystem.

So assuming you created a new slice of the correct size.
You should be able to mirror the existing slice to the new slice. Then mount the virtual device representing the mirror.
You do have to always use the mirror through the virtual /dev/md device, not the raw slices.

The raw slices making up the mirror are perfectly ordinary UFS partitions. So yes they will be recognised.
But if you modify one directly instead of through the virtual device, you changes won't be mirrored to the other.

But yes, if a disk fails. You can use the other slice directly if necessary. But normally you would just keep using the metadevice.
And if you metaoffline a disk. You could then back it up.
But backups are normally more conveniently done with fssnap. That way you don't have to split mirrors and join them again.

That's very valuable information. I hesitated when I read the question because, like you, I was unsure of the implications - thanks for clarifying and have a star for doing so!

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