On Sun, 19 Jul 2009, Martin wrote:
I don't see much similarity between mirroring and raidz other than
that they both support redundancy.
A single parity device against a single data device is, in essence,
mirroring. For all intents and purposes, raid and mirroring with
this configuration are one and the same.
Try creating a raidz pool with two drives (or files), pull one of the
drives, and see what happens. Then try the same with mirroring. Do
they behave the same? I expect not ...
I am not sure if raidz even allows you to create pool with just two
drives.
The point simply was that it might be straightforward to add a
device and convert a raidz array into a raidz2 array, which
effectively would be adding a parity device. An extension of that
is to convert a raidz2 array back into a raidz array and increase
its size without adding a device.
That would be nice. Before developers worry about such exotic
features, I would rather that they attend to the gross performance
issues so that zfs performs at least as well as Windows NTFS or Linux
XFS in all common cases.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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