Setting up ZFS - Filesystem Properties and Installing on Root

[APseudoUtopia]

On Tue, Nov 22, 2011 at 3:06 AM, Matthew Seaman
<m.seaman at infracaninophile.co.uk> wrote:
> On 22/11/2011 02:09, APseudoUtopia wrote:
>> Another quick question about swap: If I have 4 drives, with 512MB
>> swap, the system uses all 4 swap partitions, correct? So it's not like
>> it'd be going to waste? I'd have a total of 2 GB swap?
>
> Well, yes.  If you just declare those raw partitions to be swap areas,
> that will be the case.  However, doing this is asking for trouble: you
> subvert any resilience features obtained by using ZFS with raidz1.  If
> any one of the drives fails, your swap area will break and your system
> will probably crash.
>
> Better to set up two pairs of gmirrors for swap -- the procedure is
> described here: http://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/Mirror
> in section3 "Finish Install."  This will effectively give you a raid10
> for your swap, with a total size of 1GB.
>

I'm not sure I understand this. How would that negatively affect the
raidz1? The swap isn't in the zpool. I understand the system may crash
if the OS was using the swap space and the drive failed. But would you
not be able to reboot into a degraded zpool state and still have a
usable system?