On Oct 19, 2012, at 12:16 AM, James C. McPherson <j...@opensolaris.org> wrote:

> On 19/10/12 04:50 PM, Jim Klimov wrote:
>> Hello all,
>> I have one more thought - or a question - about the current
>> strangeness of rpool import: is it supported, or does it work,
>> to have rpools on multipathed devices?
>> If yes (which I hope it is, but don't have a means to check)
>> what sort of a string is saved into the pool's labels as its
>> device path? Some metadevice which is on a layer above mpxio,
>> or one of the physical storage device paths? If the latter is
>> the case, what happens during system boot if the multipathing
>> happens to choose another path, not the one saved in labels?
> if you run /usr/bin/strings over /etc/zfs/zpool.cache,
> you'll see that not only is the device path stored, but
> (more importantly) the devid.

yuk. "zdb -C" is what you want.

> As far as I'm aware, having an rpool on multipathed devices
> is fine. Multiple paths to the device should still allow ZFS
> to obtain the same devid info... and we use devid's in
> preference to physical paths.

It is fine. The boot process is slightly different in that zpool.cache
is not consulted at first. However, it is consulted later, so there are
edge cases where this can cause problems when there are significant
changes in the device tree. The archives are full of workarounds for 
this rare case.
 -- richard



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