[OpenIndiana-discuss] rpool defragmentation

[Timothy Coalson]

On Fri, Jan 16, 2015 at 11:47 AM, Andrew Gabriel <
illumos at cucumber.demon.co.uk> wrote:

> On 01/16/15 03:47 PM, Gary Gendel wrote:
>
>> On 01/16/2015 10:22 AM, Andrew Gabriel wrote:
>>
>>> On 01/16/15 02:37 PM, Gary Gendel wrote:
>>>
>>>>
>>>>  I thought about creating a new BE and then sending the current BE to
>>>> it, but there doesn't seem to be enough room.
>>>>
>>>
>>> Since rpool can only be either a single disk or a mirror, the easiest
>>> way to defrag it is to attach another mirror side and let it resilver. The
>>> new mirror side will be defragged. Make sure the new disk is bootable (has
>>> grub etc on it), and then zpool split off the old disk. It would be a good
>>> opportunity to move to a bigger rpool disk too.
>>>
>>>  Yes, this is the rpool and is mirrored.  Would resilvering really
>> defragment it?
>>
>
> Yes, space is allocated afresh when resilvering (which is a significant
> difference from traditional RAID).


I find that surprising.  Does the metadata on the older drive(s) manage to
refer to the new, independent location of the blocks on the new mirror, and
if so, how?