[OpenIndiana-discuss] data on rpool - Bad idea?

[Harry Putnam]

I've read that it is a bad idea to have datasets on the same disc
that rpool is on.  I'm not sure why that is so.

In my current situation I need more space but to rig up my
`HP xw8600 workstation' with more disc space will require getting a cage
and some new discs, not to mention the huffing and puffing necessary
to get it all installed and usable.

When I installed oi on this hardware I thought it was a smart idea to
use 2 older 250 GB discs for a 2 disc mirrored setup of rpool.  And a
pair of 1tb discs for 2disc mirror of datasets.

At that time I hadn't really realized what it would take to add
discs. 

But of course I'm now running out of space... and still not flush
enough to pop for the $400 or so to add a cage and 4 2-3 tb discs.

However I do have 2 1tb discs laying unused.

So, (finally cutting to chase) how bad of an idea would it be to use
those two 1tb discs for a mirrored rpool and whatever data.

I would gain about 800-850 GB of mirrored data space but it would
involve putting data on same discs and rpool.

(I'll leave for another thread to discuss how to get rpool onto the new
discs in the most painless manner)

So, what are your best thoughts on employing the two 1tb discs as
described above?