zfs on gmirror slice

[Pete French]

> ZFS includes support for RAID0 (stripe), RAID1 (mirroring), RAID5 and RAID6
> (raidz1/raidz2), and (soon in OpenSolaris) RAID7 (raidz3).  Why would you
> want to build a pool out of devices that are already RAID'd together?

Because gmirror type RAIDing is more appropriate for your application
than ZFS RAID ? I am not the original poster, but I can easily
see why one would want to do do this. For example making a gmirror
of a local drive and a remote drive - you can ask gmirror to prefer
reads on the local disc, but there isn't a way to specify that
in ZFS that I know of. Also gmirror on top of ggate behaves nicely if
the remote drive fails. ZFS does not behave nicely at all - or it didn't
when I ran tests. I havent tried on the latest version I admit.

But ZFS as a filesystem still has many significant advantages, so
runnng it on top of gmirror is actually a worthwhile thing to do.

-pete.