Mirror of Raidz for data reliability

[Daniel Kalchev]

On 18.05.12 19:55, Trent Nelson wrote:
> So, my thinking isŠ because both machines can see all disks, the 
> master could import the zpool as normal, and the slave could import it 
> read-only. (Or not import it at all...)

The proper way of doing it is "not import it at all". ZFS is not an 
shared filesystem.

If you have the second host mount the zpool even if read-only, you only 
guarantee that data on the pool will not be corrupted, but you cannot 
avoid the second "read-only" host panic or otherwise crash if it tries 
to access data which is no longer where it thinks it is, because the 
second host doesn't have access to the primary host's in-memory metadata 
about ZFS. Since ZFS is copy on write filesystem, chances are you will 
be accessing data that is no longer valid. Refreshing the internal ZFS 
state between two or more hosts is non-trivial (if it was, Sun would 
have done this, as it suits their usage) and in any case performance 
will suffer at least as much as an true networked filesystem does, 
compared to "native" ZFS.

Daniel